diff --git a/metadata/dependency_metadata.py b/metadata/dependency_metadata.py
index 79d746208..12755c84a 100644
--- a/metadata/dependency_metadata.py
+++ b/metadata/dependency_metadata.py
@@ -6,7 +6,7 @@
 from collections import defaultdict
 import os
 import sys
-from typing import Dict, List, Set, Tuple
+from typing import Dict, List, Set, Tuple, Union, Optional, Literal, Any
 
 _THIS_DIR = os.path.abspath(os.path.dirname(__file__))
 # The repo's root directory.
@@ -24,7 +24,19 @@ import metadata.validation_result as vr
 
 
 class DependencyMetadata:
-    """The metadata for a single dependency."""
+    """The metadata for a single dependency.
+
+       See @property declarations below to retrieve validated fields for
+       downstream consumption.
+
+       The property returns `None` if the provided value (e.g. in
+       README.chromium file) is clearly invalid.
+
+       Otherwise, it returns a suitably typed value (see comments on each
+       property).
+
+       To retrieve unvalidated (i.e. raw values) fields, use get_entries().
+    """
 
     # Fields that are always required.
     _MANDATORY_FIELDS = {
@@ -171,9 +183,11 @@ class DependencyMetadata:
         version_value = self._metadata.get(known_fields.VERSION)
         date_value = self._metadata.get(known_fields.DATE)
         revision_value = self._metadata.get(known_fields.REVISION)
-        if ((not version_value or version_util.is_unknown(version_value))
-                and (not date_value or util.is_unknown(date_value))
-                and (not revision_value or util.is_unknown(revision_value))):
+        if ((not version_value
+             or version_util.version_is_unknown(version_value)) and
+            (not date_value or version_util.version_is_unknown(date_value))
+                and (not revision_value
+                     or version_util.version_is_unknown(revision_value))):
             versioning_fields = [
                 known_fields.VERSION, known_fields.DATE, known_fields.REVISION
             ]
@@ -199,3 +213,105 @@ class DependencyMetadata:
                 results.append(result)
 
         return results
+
+    def _return_as_property(self, field: field_types.MetadataField) -> Any:
+        """Helper function to create a property for DependencyMetadata.
+
+        The property accessor will validate and return sanitized field value.
+        """
+        assert field in known_fields.ALL_FIELDS
+
+        raw_value = self._metadata.get(field, None)
+        if raw_value is None:
+            # Field is not set.
+            return None
+
+        return field.narrow_type(raw_value)
+
+    @property
+    def name(self) -> Optional[str]:
+        return self._return_as_property(known_fields.NAME)
+
+    @property
+    def short_name(self) -> Optional[str]:
+        return self._return_as_property(known_fields.SHORT_NAME)
+
+    @property
+    def url(self) -> Optional[List[str]]:
+        """
+        Returns a list of URLs that points to upstream repo.
+        The URLs are guaranteed to `urllib.parse.urlparse` without errors.
+
+        Returns None if this repository is the canonical repository of this
+        dependency (see is_canonical below).
+        """
+        return self._return_as_property(known_fields.URL)
+
+    @property
+    def is_canonical(self) -> bool:
+        """
+        Returns whether this repository is the canonical public repository of this dependency.
+
+        This is derived from a special value in the URL field.
+        """
+        value = self._metadata.get(known_fields.URL, "")
+        return known_fields.URL.repo_is_canonical(value)
+
+    @property
+    def version(self) -> Optional[str]:
+        return self._return_as_property(known_fields.VERSION)
+
+    @property
+    def date(self) -> Optional[str]:
+        """Returns in "YYYY-MM-DD" format."""
+        return self._return_as_property(known_fields.DATE)
+
+    @property
+    def revision(self) -> Optional[str]:
+        return self._return_as_property(known_fields.REVISION)
+
+    @property
+    def license(self) -> Optional[List[str]]:
+        """Returns a list of license names."""
+        return self._return_as_property(known_fields.LICENSE)
+
+    @property
+    def license_file(self) -> Optional[List[str]]:
+        # TODO(b/321154076): Consider excluding files that doesn't exist on
+        # disk if it's not too hard.
+        #
+        # Plumbing src_root and dependency_dir into field validator is
+        # required.
+        return self._return_as_property(known_fields.LICENSE_FILE)
+
+    @property
+    def security_critical(self) -> Optional[bool]:
+        return self._return_as_property(known_fields.SECURITY_CRITICAL)
+
+    @property
+    def shipped(self) -> Optional[bool]:
+        return self._return_as_property(known_fields.SHIPPED)
+
+    @property
+    def shipped_in_chromium(self) -> Optional[bool]:
+        return self._return_as_property(known_fields.SHIPPED_IN_CHROMIUM)
+
+    @property
+    def license_android_compatible(self) -> Optional[bool]:
+        return self._return_as_property(known_fields.LICENSE_ANDROID_COMPATIBLE)
+
+    @property
+    def cpe_prefix(self) -> Optional[str]:
+        """Returns a lowercase string (CPE names are case-insensitive)."""
+        return self._return_as_property(known_fields.CPE_PREFIX)
+
+    @property
+    def description(self) -> Optional[str]:
+        return self._return_as_property(known_fields.DESCRIPTION)
+
+    @property
+    def local_modifications(self) -> Optional[Union[Literal[False], str]]:
+        """Returns `False` if there's no local modifications.
+           Otherwise the text content extracted from the metadata.
+        """
+        return self._return_as_property(known_fields.LOCAL_MODIFICATIONS)
diff --git a/metadata/fields/custom/cpe_prefix.py b/metadata/fields/custom/cpe_prefix.py
index 6481af796..3bcef029e 100644
--- a/metadata/fields/custom/cpe_prefix.py
+++ b/metadata/fields/custom/cpe_prefix.py
@@ -68,12 +68,15 @@ class CPEPrefixField(field_types.SingleLineTextField):
     def __init__(self):
         super().__init__(name="CPEPrefix")
 
+    def _is_valid(self, value: str) -> bool:
+        return (util.is_unknown(value) or is_formatted_string_cpe(value)
+                or is_uri_cpe(value))
+
     def validate(self, value: str) -> Optional[vr.ValidationResult]:
         """Checks the given value is either 'unknown', or conforms to
         either the CPE 2.3 or 2.2 format.
         """
-        if (util.is_unknown(value) or is_formatted_string_cpe(value)
-                or is_uri_cpe(value)):
+        if self._is_valid(value):
             return None
 
         return vr.ValidationError(
@@ -85,3 +88,13 @@ class CPEPrefixField(field_types.SingleLineTextField):
                 "https://nvd.nist.gov/products/cpe/search.",
                 f"Current value: '{value}'.",
             ])
+
+    def narrow_type(self, value: str) -> Optional[str]:
+        if not self._is_valid(value):
+            return None
+
+        # CPE names are case-insensitive, we normalize to lowercase.
+        # See https://cpe.mitre.org/specification/.
+        value = value.lower()
+
+        return value
diff --git a/metadata/fields/custom/date.py b/metadata/fields/custom/date.py
index 25d88996f..a5a120799 100644
--- a/metadata/fields/custom/date.py
+++ b/metadata/fields/custom/date.py
@@ -6,7 +6,7 @@
 import datetime
 import os
 import sys
-from typing import Optional
+from typing import Optional, Tuple
 
 _THIS_DIR = os.path.abspath(os.path.dirname(__file__))
 # The repo's root directory.
@@ -59,13 +59,65 @@ _RECOGNIZED_DATE_FORMATS = (
 )
 
 
-def format_matches(value: str, date_format: str):
-    """Returns whether the given value matches the date format."""
+def parse_with_format(value: str,
+                      date_format: str) -> Optional[datetime.datetime]:
+    """Returns datetime object if `value` can be parsed with `date_format`"""
     try:
-        datetime.datetime.strptime(value, date_format)
+        return datetime.datetime.strptime(value, date_format)
     except ValueError:
-        return False
-    return True
+        return None
+
+
+def to_preferred_format(dt: datetime.datetime) -> str:
+    return datetime.datetime.strftime(dt, _PREFERRED_PREFIX_FORMAT)
+
+
+def parse_date(value: str) -> Optional[Tuple[str, bool]]:
+    """Try to parse value into a YYYY-MM-DD date.
+
+       If successful: returns (str, int).
+       - The str is guaranteed to be in YYYY-MM-DD format.
+       - The bool indicates whether `value` is ambiguous.
+         For example, "2020/03/05" matches both "YYYY/MM/DD" and "YYYY/DD/MM".
+    """
+    matches = []
+    value = value.strip()
+    if not value:
+        return None
+
+    first_part = value.split()[0]
+
+    # Try to match preferred prefix.
+    if dt := parse_with_format(first_part, _PREFERRED_PREFIX_FORMAT):
+        matches.append(dt)
+
+    if not matches:
+        # Try alternative prefix formats.
+        for date_format in _RECOGNIZED_PREFIX_FORMATS:
+            if dt := parse_with_format(first_part, date_format):
+                matches.append(dt)
+
+    if not matches:
+        # Try matching the complete string.
+        for date_format in _RECOGNIZED_DATE_FORMATS:
+            if dt := parse_with_format(value, date_format):
+                matches.append(dt)
+
+    if not matches:
+        # Try ISO 8601.
+        try:
+            dt = datetime.datetime.fromisoformat(value)
+            matches.append(dt)
+        except ValueError:
+            pass
+
+    if not matches:
+        return None
+
+    # Determine if the value is parsed without ambiguity.
+    is_ambiguous = len(set(map(to_preferred_format, matches))) > 1
+
+    return to_preferred_format(matches[0]), is_ambiguous
 
 
 class DateField(field_types.SingleLineTextField):
@@ -81,32 +133,29 @@ class DateField(field_types.SingleLineTextField):
                 reason=f"{self._name} is empty.",
                 additional=["Provide date in format YYYY-MM-DD."])
 
-        # Check if the first part (to ignore timezone info) uses the
-        # preferred format.
-        parts = value.split()
-        if format_matches(parts[0], _PREFERRED_PREFIX_FORMAT):
+        if not (parsed := parse_date(value)):
+            return vr.ValidationError(
+                reason=f"{self._name} is invalid.",
+                additional=["Use YYYY-MM-DD.", f"Current value is '{value}'."])
+
+        parsed_date, is_ambiguous = parsed
+        if is_ambiguous:
+            return vr.ValidationError(
+                reason=f"{self._name} is ambiguous.",
+                additional=["Use YYYY-MM-DD.", f"Current value is '{value}'."])
+
+        if not parse_with_format(value, _PREFERRED_PREFIX_FORMAT):
+            return vr.ValidationWarning(
+                reason=f"{self._name} isn't using the canonical format.",
+                additional=["Use YYYY-MM-DD.", f"Current value is '{value}'."])
+
+        return None
+
+    def narrow_type(self, value: str) -> Optional[str]:
+        """Returns ISO 8601 date string, guarantees to be YYYY-MM-DD or None."""
+        if not (parsed := parse_date(value)):
             return None
 
-        # Check if the first part (to ignore timezone info) uses a
-        # recognized format.
-        for prefix_format in _RECOGNIZED_PREFIX_FORMATS:
-            if format_matches(parts[0], prefix_format):
-                return vr.ValidationWarning(
-                    reason=f"{self._name} is not in the preferred format.",
-                    additional=[
-                        "Use YYYY-MM-DD.", f"Current value is '{value}'."
-                    ])
-
-        # Check the entire value for recognized date formats.
-        for date_format in _RECOGNIZED_DATE_FORMATS:
-            if format_matches(value, date_format):
-                return vr.ValidationWarning(
-                    reason=f"{self._name} is not in the preferred format.",
-                    additional=[
-                        "Use YYYY-MM-DD.", f"Current value is '{value}'."
-                    ])
-
-        # Return an error as the value's format was not recognized.
-        return vr.ValidationError(
-            reason=f"{self._name} is invalid.",
-            additional=["Use YYYY-MM-DD.", f"Current value is '{value}'."])
+        # We still return a date even if the parsing result is ambiguous. An
+        # date that's a few month off is better than nothing at all.
+        return parsed[0]
diff --git a/metadata/fields/custom/license.py b/metadata/fields/custom/license.py
index 713ee2258..d1e3578d2 100644
--- a/metadata/fields/custom/license.py
+++ b/metadata/fields/custom/license.py
@@ -49,6 +49,11 @@ _PATTERN_LICENSE_ALLOWED = re.compile(
 
 _PATTERN_VERBOSE_DELIMITER = re.compile(r" and | or | / ")
 
+# Split on the canonical delimiter, or any of the non-canonical delimiters.
+_PATTERN_SPLIT_LICENSE = re.compile("{}|{}".format(
+    _PATTERN_VERBOSE_DELIMITER.pattern,
+    field_types.MetadataField.VALUE_DELIMITER))
+
 
 def process_license_value(value: str,
                           atomic_delimiter: str) -> List[Tuple[str, bool]]:
@@ -134,3 +139,11 @@ class LicenseField(field_types.SingleLineTextField):
                 reason=f"Separate licenses using a '{self.VALUE_DELIMITER}'.")
 
         return None
+
+    def narrow_type(self, value: str) -> Optional[List[str]]:
+        if not value:
+            # Empty License field is equivalent to "not declared".
+            return None
+
+        parts = _PATTERN_SPLIT_LICENSE.split(value)
+        return list(filter(bool, map(lambda str: str.strip(), parts)))
diff --git a/metadata/fields/custom/local_modifications.py b/metadata/fields/custom/local_modifications.py
index 1b1912a60..82e859118 100644
--- a/metadata/fields/custom/local_modifications.py
+++ b/metadata/fields/custom/local_modifications.py
@@ -6,6 +6,7 @@
 import os
 import re
 import sys
+from typing import Optional, Union, Literal
 
 _THIS_DIR = os.path.abspath(os.path.dirname(__file__))
 # The repo's root directory.
@@ -39,13 +40,28 @@ class LocalModificationsField(field_types.FreeformTextField):
     def __init__(self):
         super().__init__(name="Local Modifications", structured=False)
 
-    def should_terminate_field(self, field_value) -> bool:
-        field_value = field_value.strip()
+    def _is_no_modification(self, value) -> bool:
+        for pattern in _PATTERNS_NOT_MODIFIED:
+            if pattern.match(value):
+                return True
+
+        return False
+
+    def should_terminate_field(self, value) -> bool:
+        value = value.strip()
 
         # If we can reasonably infer the field value means "No modification",
         # terminate this field to avoid over extraction.
-        for pattern in _PATTERNS_NOT_MODIFIED:
-            if pattern.match(field_value):
-                return True
+        if self._is_no_modification(value):
+            return True
 
         return False
+
+    def narrow_type(self, value) -> Optional[Union[Literal[False], str]]:
+        if not value:
+            return False
+
+        if self._is_no_modification(value):
+            return False
+
+        return value
diff --git a/metadata/fields/custom/revision.py b/metadata/fields/custom/revision.py
new file mode 100644
index 000000000..4ffa6df57
--- /dev/null
+++ b/metadata/fields/custom/revision.py
@@ -0,0 +1,41 @@
+#!/usr/bin/env python3
+# Copyright 2024 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import os
+import re
+import sys
+from typing import Optional
+
+_THIS_DIR = os.path.abspath(os.path.dirname(__file__))
+# The repo's root directory.
+_ROOT_DIR = os.path.abspath(os.path.join(_THIS_DIR, "..", "..", ".."))
+
+# Add the repo's root directory for clearer imports.
+sys.path.insert(0, _ROOT_DIR)
+
+import metadata.fields.field_types as field_types
+import metadata.fields.custom.version as version_field
+import metadata.fields.util as util
+import metadata.validation_result as vr
+
+
+class RevisionField(field_types.SingleLineTextField):
+    """Custom field for the revision."""
+
+    def __init__(self):
+        super().__init__(name="Revision")
+
+    def narrow_type(self, value: str) -> Optional[str]:
+        value = super().narrow_type(value)
+        if not value:
+            return None
+
+        if version_field.version_is_unknown(value):
+            return None
+
+        if util.is_known_invalid_value(value):
+            return None
+
+        return value
diff --git a/metadata/fields/custom/url.py b/metadata/fields/custom/url.py
index e1cc96ed0..2dfb7319b 100644
--- a/metadata/fields/custom/url.py
+++ b/metadata/fields/custom/url.py
@@ -6,7 +6,9 @@
 import os
 import re
 import sys
-from typing import Optional
+from typing import Optional, List
+from urllib.parse import urlparse, urlunparse
+from itertools import filterfalse
 
 _THIS_DIR = os.path.abspath(os.path.dirname(__file__))
 # The repo's root directory.
@@ -19,29 +21,73 @@ import metadata.fields.field_types as field_types
 import metadata.fields.util as util
 import metadata.validation_result as vr
 
-_PATTERN_URL_ALLOWED = re.compile(r"^(https?|ftp|git):\/\/\S+$")
 _PATTERN_URL_CANONICAL_REPO = re.compile(
     r"^This is the canonical (public )?repo(sitory)?\.?$", re.IGNORECASE)
 
+_SUPPORTED_SCHEMES = {
+    'http',
+    'https',
+    'git',
+    'ftp',
+}
+
+# URLs can't contain whitespaces. Treat them as delimiters so we can handle cases where URL field contains one URL per line (without comma delimiter).
+_PATTERN_URL_DELIMITER = re.compile("{}|{}".format(
+    r'\s+', field_types.MetadataField.VALUE_DELIMITER))
+
+
+def _split_urls(value: str) -> List[str]:
+    """Split url field value into individual URLs."""
+    urls = _PATTERN_URL_DELIMITER.split(value)
+    return list(filter(lambda x: len(x) > 0, map(str.strip, urls)))
+
+
+def _url_canonicalize(url: str) -> str:
+    """Return the canonicalized URL (e.g. make scheme lower case)."""
+    return urlunparse(urlparse(url))
+
+
+def _url_is_canonical(url: str) -> bool:
+    return url == _url_canonicalize(url)
+
+
+def _url_is_valid(url: str) -> bool:
+    """Checks whether the given `url` is acceptable:
+       * url is can be parsed without an error.
+       * url uses a supported scheme / protocol.
+    """
+    try:
+        u = urlparse(url)
+    except:
+        return False
+
+    if u.scheme not in _SUPPORTED_SCHEMES:
+        return False
+
+    return True
 
 class URLField(field_types.MetadataField):
     """Custom field for the package URL(s)."""
     def __init__(self):
         super().__init__(name="URL")
 
+    def repo_is_canonical(self, value: str):
+        """Returns if `raw_value` indicates this repository is the canonical repository."""
+        return util.matches(_PATTERN_URL_CANONICAL_REPO, value.strip())
+
     def validate(self, value: str) -> Optional[vr.ValidationResult]:
         """Checks the given value has acceptable URL values only.
 
         Note: this field supports multiple values.
         """
-        if util.matches(_PATTERN_URL_CANONICAL_REPO, value):
+        if self.repo_is_canonical(value):
             return None
 
-        invalid_values = []
-        for url in value.split(self.VALUE_DELIMITER):
-            url = url.strip()
-            if not util.matches(_PATTERN_URL_ALLOWED, url):
-                invalid_values.append(url)
+        urls = _split_urls(value)
+        if not urls:
+            return vr.ValidationError(reason=f"{self._name} must be provided.")
+
+        invalid_values = list(filterfalse(_url_is_valid, urls))
 
         if invalid_values:
             return vr.ValidationError(
@@ -53,4 +99,26 @@ class URLField(field_types.MetadataField):
                     f"Invalid values: {util.quoted(invalid_values)}.",
                 ])
 
+        non_canon_values = list(filterfalse(_url_is_canonical, urls))
+        if non_canon_values:
+            canon_values = list(map(_url_canonicalize, non_canon_values))
+            return vr.ValidationWarning(
+                reason=f"{self._name} is contains non-canonical URLs.",
+                additional=[
+                    "URLs should be canonical and well-formed."
+                    f"Non canonical values: {util.quoted(non_canon_values)}.",
+                    f"Canonicalized URLs should be: {util.quoted(canon_values)}."
+                ])
+
         return None
+
+    def narrow_type(self, value) -> Optional[List[str]]:
+        if not value:
+            return None
+
+        if self.repo_is_canonical(value):
+            return None
+
+        # Filter out invalid URLs, and canonicalize the URLs.
+        return list(
+            map(_url_canonicalize, filter(_url_is_valid, _split_urls(value))))
diff --git a/metadata/fields/custom/version.py b/metadata/fields/custom/version.py
index 9d78c954a..068676946 100644
--- a/metadata/fields/custom/version.py
+++ b/metadata/fields/custom/version.py
@@ -19,17 +19,16 @@ import metadata.fields.field_types as field_types
 import metadata.fields.util as util
 import metadata.validation_result as vr
 
-_PATTERN_NOT_APPLICABLE = re.compile(r"^N ?\/ ?A$", re.IGNORECASE)
 
-
-def is_unknown(value: str) -> bool:
+def version_is_unknown(value: str) -> bool:
     """Returns whether the value denotes the version being unknown."""
-    return (value == "0" or util.matches(_PATTERN_NOT_APPLICABLE, value)
+    return (value == "0" or util.is_not_applicable(value)
             or util.is_unknown(value))
 
 
 class VersionField(field_types.SingleLineTextField):
     """Custom field for the package version."""
+
     def __init__(self):
         super().__init__(name="Version")
 
@@ -55,3 +54,16 @@ class VersionField(field_types.SingleLineTextField):
                 ])
 
         return None
+
+    def narrow_type(self, value: str) -> Optional[str]:
+        value = super().narrow_type(value)
+        if not value:
+            return None
+
+        if version_is_unknown(value):
+            return None
+
+        if util.is_known_invalid_value(value):
+            return None
+
+        return value
diff --git a/metadata/fields/field_types.py b/metadata/fields/field_types.py
index cb5623152..c74af66bb 100644
--- a/metadata/fields/field_types.py
+++ b/metadata/fields/field_types.py
@@ -7,6 +7,7 @@ import os
 import re
 import sys
 from typing import Optional
+from enum import Enum
 
 _THIS_DIR = os.path.abspath(os.path.dirname(__file__))
 # The repo's root directory.
@@ -26,7 +27,6 @@ _PATTERN_YES_OR_NO = re.compile(r"^(yes|no)$", re.IGNORECASE)
 # case-insensitive. e.g. "No (test only)", "Yes?"
 _PATTERN_STARTS_WITH_YES_OR_NO = re.compile(r"^(yes|no)", re.IGNORECASE)
 
-
 class MetadataField:
     """Base class for all metadata fields."""
 
@@ -73,6 +73,15 @@ class MetadataField:
         """
         raise NotImplementedError(f"{self._name} field validation not defined.")
 
+    def narrow_type(self, value):
+        """Returns a narrowly typed (e.g. bool) value for this field for
+           downstream consumption.
+
+           The alternative being the downstream parses the string again.
+        """
+        raise NotImplementedError(
+            f"{self._name} field value coersion not defined.")
+
 
 class FreeformTextField(MetadataField):
     """Field where the value is freeform text."""
@@ -86,6 +95,9 @@ class FreeformTextField(MetadataField):
 
         return None
 
+    def narrow_type(self, value):
+        assert value is not None
+        return value
 
 class SingleLineTextField(FreeformTextField):
     """Field where the field as a whole is a single line of text."""
@@ -126,3 +138,6 @@ class YesNoField(SingleLineTextField):
                 f"This field must be {util.YES} or {util.NO}.",
                 f"Current value is '{value}'.",
             ])
+
+    def narrow_type(self, value) -> Optional[bool]:
+        return util.infer_as_boolean(super().narrow_type(value))
diff --git a/metadata/fields/known.py b/metadata/fields/known.py
index 4d69a161c..6f97fccfc 100644
--- a/metadata/fields/known.py
+++ b/metadata/fields/known.py
@@ -21,12 +21,12 @@ import metadata.fields.custom.license_file
 import metadata.fields.custom.local_modifications
 import metadata.fields.custom.url
 import metadata.fields.custom.version
+import metadata.fields.custom.revision
 import metadata.fields.field_types as field_types
 
 # Freeform text fields.
 NAME = field_types.SingleLineTextField("Name")
 SHORT_NAME = field_types.SingleLineTextField("Short Name")
-REVISION = field_types.SingleLineTextField("Revision")
 DESCRIPTION = field_types.FreeformTextField("Description", structured=False)
 
 # Yes/no fields.
@@ -43,6 +43,7 @@ LICENSE = metadata.fields.custom.license.LicenseField()
 LICENSE_FILE = metadata.fields.custom.license_file.LicenseFileField()
 URL = metadata.fields.custom.url.URLField()
 VERSION = metadata.fields.custom.version.VersionField()
+REVISION = metadata.fields.custom.revision.RevisionField()
 LOCAL_MODIFICATIONS = metadata.fields.custom.local_modifications.LocalModificationsField(
 )
 
diff --git a/metadata/fields/util.py b/metadata/fields/util.py
index 4c51ba7a9..9c256f8c0 100644
--- a/metadata/fields/util.py
+++ b/metadata/fields/util.py
@@ -26,6 +26,22 @@ _PATTERN_STARTS_WITH_YES = re.compile(r"^yes", re.IGNORECASE)
 # case-insensitive.
 _PATTERN_STARTS_WITH_NO = re.compile(r"^no", re.IGNORECASE)
 
+# Variants of N/A (Not Applicable).
+_PATTERN_NOT_APPLICABLE = re.compile(r"^(N ?\/ ?A)\.?|na\.?|not applicable\.?$",
+                                     re.IGNORECASE)
+
+# A collection of values that provides little information.
+# Use lower-case for easier comparison.
+_KNOWN_INVALID_VALUES = {
+    "0",
+    "varies",
+    "-",
+    "unknown",
+    "head",
+    "see deps",
+    "deps",
+}
+
 
 def matches(pattern: re.Pattern, value: str) -> bool:
     """Returns whether the value matches the pattern."""
@@ -61,3 +77,20 @@ def infer_as_boolean(value: str, default: bool = True) -> bool:
         return False
     else:
         return default
+
+
+def is_known_invalid_value(value: str):
+    """Returns whether `value` is among the known bad values that provides
+       little machine readable information.
+    """
+    if not value:
+        return False
+
+    if value.lower() in _KNOWN_INVALID_VALUES:
+        return True
+
+    return False
+
+
+def is_not_applicable(value: str) -> bool:
+    return matches(_PATTERN_NOT_APPLICABLE, value)
diff --git a/metadata/tests/fields_test.py b/metadata/tests/fields_test.py
index 263a8c478..e2214bc09 100644
--- a/metadata/tests/fields_test.py
+++ b/metadata/tests/fields_test.py
@@ -95,17 +95,18 @@ class FieldValidationTest(unittest.TestCase):
     def test_date_validation(self):
         self._run_field_validation(
             field=known_fields.DATE,
-            valid_values=[
-                "2012-03-04", "2012-03-04 UTC", "2012-03-04 UTC+10:00"
-            ],
+            valid_values=["2012-03-04"],
             error_values=[
                 "",
                 "\n",
                 "N/A",
+                "03-04-12",  # Ambiguous month and day.
+                "04/03/2012",  # Ambiguous month and day.
             ],
             warning_values=[
+                "2012-03-04 UTC", "2012-03-04 UTC+10:00",
                 "2012/03/04 UTC+10:00", "20120304", "April 3, 2012",
-                "3 Apr 2012", "03-04-12", "04/03/2012",
+                "3 Apr 2012", "30/12/2000", "20-03-2020",
                 "Tue Apr 3 05:06:07 2012 +0800"
             ],
         )
@@ -181,14 +182,18 @@ class FieldValidationTest(unittest.TestCase):
                 "https://www.example.com/a",
                 "http://www.example.com/b",
                 "ftp://www.example.com/c,git://www.example.com/d",
+                "https://www.example.com/a\n  https://example.com/b",
                 "This is the canonical public repository",
             ],
+            warning_values=[
+                # Scheme is case-insensitive, but should be lower case.
+                "Https://www.example.com/g",
+            ],
             error_values=[
                 "",
                 "\n",
                 "ghttps://www.example.com/e",
                 "https://www.example.com/ f",
-                "Https://www.example.com/g",
                 "This is an unrecognized message for the URL",
             ],
         )
diff --git a/metadata/tests/type_narrowing_test.py b/metadata/tests/type_narrowing_test.py
new file mode 100644
index 000000000..8f84f8668
--- /dev/null
+++ b/metadata/tests/type_narrowing_test.py
@@ -0,0 +1,187 @@
+#!/usr/bin/env python3
+# Copyright 2024 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import os
+import sys
+import unittest
+from typing import Any, Callable
+
+_THIS_DIR = os.path.abspath(os.path.dirname(__file__))
+# The repo's root directory.
+_ROOT_DIR = os.path.abspath(os.path.join(_THIS_DIR, "..", ".."))
+
+# Add the repo's root directory for clearer imports.
+sys.path.insert(0, _ROOT_DIR)
+
+from metadata.fields.field_types import MetadataField
+import metadata.fields.known as fields
+from metadata.dependency_metadata import DependencyMetadata
+
+
+class FieldValidationTest(unittest.TestCase):
+    """Tests narrow_type() on fields we validate and extract structural data."""
+
+    def _test_on_field(self, field: MetadataField) -> Callable:
+
+        def expect(value: str, expected_value: Any, reason: str):
+            output = field.narrow_type(value)
+            self.assertEqual(
+                output, expected_value,
+                f'Field "{field.get_name()}" should {reason}. Input value'
+                f' was: "{value}", but got coerced into {repr(output)}')
+
+        return expect
+
+    def test_name(self):
+        expect = self._test_on_field(fields.NAME)
+        expect("package name", "package name", "return as-is")
+        expect("", "", "not coerce empty string to `None`")
+
+    def test_short_name(self):
+        expect = self._test_on_field(fields.SHORT_NAME)
+        expect("pkg-name", "pkg-name", "return as-is")
+        expect("", "", "not coerce empty string to `None`")
+
+    def test_url(self):
+        expect = self._test_on_field(fields.URL)
+        expect("", None, "treat empty string as None")
+        expect("https://example.com/", ["https://example.com/"],
+               "return valid url")
+        expect("https://example.com/,\nhttps://example2.com/",
+               ["https://example.com/", "https://example2.com/"],
+               "return multiple valid urls")
+        expect("file://test", [], "reject unsupported scheme")
+        expect("file://test,\nhttps://example.com", ["https://example.com"],
+               "reject unsupported scheme")
+        expect("HTTPS://example.com", ["https://example.com"],
+               "canonicalize url")
+        expect("http", [], "reject invalid url")
+        expect("This is the canonical repo.", None,
+               "understand the this repo is canonical message")
+
+    def test_version(self):
+        expect = self._test_on_field(fields.VERSION)
+        expect("", None, "treat empty string as None")
+        expect("0", None, "treat invalid value as None")
+        expect("varies", None, "treat invalid value as None")
+        expect("see deps", None, "treat invalid value as None")
+        expect("N/A", None, "N/A is treated as None")
+        expect("Not applicable.", None, "N/A is treated as None")
+
+    def test_date(self):
+        expect = self._test_on_field(fields.DATE)
+        expect("", None, "treat empty string as None")
+        expect("0", None, "treat invalid value as None")
+        expect("varies", None, "treat invalid value as None")
+        expect("2024-01-02", "2024-01-02", "accepts ISO 8601 date")
+        expect("2024-01-02T03:04:05Z", "2024-01-02",
+               "accepts ISO 8601 date time")
+        expect("Jan 2 2024", "2024-01-02", "accepts locale format")
+        expect(
+            "02/03/2000", "2000-03-02",
+            "accepts ambiguous MM/DD format (better than no date info at all)")
+        expect("11/30/2000", "2000-11-30", "accepts unambiguous MM/DD format")
+
+    def test_revision(self):
+        expect = self._test_on_field(fields.REVISION)
+        expect("", None, "treat empty string as None")
+        expect("0", None, "treat invalid value as None")
+        expect("varies", None, "treat invalid value as None")
+        expect("see deps", None, "treat invalid value as None")
+        expect("N/A", None, "N/A is treated as None")
+        expect("Not applicable.", None, "N/A is treated as None")
+
+    def test_license(self):
+        expect = self._test_on_field(fields.LICENSE)
+        expect("", None, "treat empty string as None")
+        expect("LICENSE-1", ["LICENSE-1"], "return as a list")
+        expect("LGPL v2 and BSD", ["LGPL v2", "BSD"], "return as a list")
+
+    def test_license_file(self):
+        # TODO(b/321154076): Consider excluding files that doesn't exist on
+        # disk if it's not too hard.
+        #
+        # Right now, we return the unparsed license file field as-is.
+        expect = self._test_on_field(fields.LICENSE_FILE)
+        expect("src/file", "src/file", "return value as-is")
+
+    def test_security_critical(self):
+        expect = self._test_on_field(fields.SECURITY_CRITICAL)
+        expect("yes", True, "understand truthy value")
+        expect("Yes", True, "understand truthy value")
+        expect("no", False, "understand falsey value")
+        expect("No, because", False,
+               "understand falsey value, with description")
+
+    def test_shipped(self):
+        expect = self._test_on_field(fields.SHIPPED)
+        expect("yes", True, "understand truthy value")
+        expect("Yes, but", True, "understand truthy value with extra comment")
+        expect("no", False, "understand falsey value")
+        expect("no, because", False,
+               "understand falsey value, with extra comment")
+
+    def test_shipped_in_chromium(self):
+        expect = self._test_on_field(fields.SHIPPED_IN_CHROMIUM)
+        expect("yes", True, "understand truthy value")
+        expect("Yes", True, "understand truthy value")
+        expect("no", False, "understand falsey value")
+        expect("no, because", False,
+               "understand falsey value, with extra comment")
+
+    def test_license_android_compatible(self):
+        expect = self._test_on_field(fields.LICENSE_ANDROID_COMPATIBLE)
+        expect("yes", True, "understand truthy value")
+        expect("Yes", True, "understand truthy value")
+        expect("no", False, "understand falsey value")
+        expect("no, because", False,
+               "understand falsey value, with extra comment")
+
+    def test_cpe_prefix(self):
+        expect = self._test_on_field(fields.CPE_PREFIX)
+        expect("unknown", "unknown", "understand unknown")
+        expect("bad_cpe_format", None, "rejects invalid value")
+        expect("cpe:/a:d3", "cpe:/a:d3", "accept a valid cpe prefix")
+        expect("cpe:/a:D3", "cpe:/a:d3", "normalize to lowercase")
+
+    def test_description(self):
+        expect = self._test_on_field(fields.DESCRIPTION)
+        expect("desc", "desc", "return value as-is")
+
+    def test_local_modification(self):
+        expect = self._test_on_field(fields.LOCAL_MODIFICATIONS)
+        expect("none", False, "understands none")
+        expect("(none)", False, "understands none")
+        expect("not applicable", False, "understands N/A")
+        expect("", False, "treat empty string as False")
+        expect("modified X file", "modified X file",
+               "return value as-is if it doesn't mean no modification")
+
+    def test_dependency_data_return_as_property(self):
+        dm = DependencyMetadata()
+        dm.add_entry("name", "package")
+        dm.add_entry("url", "git://git@example.com,\nbad_url://example.com")
+        dm.add_entry("security critical", "no")
+        dm.add_entry("date", "2024-01-02")
+        dm.add_entry("revision", "")
+
+        self.assertEqual(dm.name, "package")
+        self.assertEqual(dm.url, ["git://git@example.com"])
+        self.assertEqual(dm.security_critical, False)
+        self.assertEqual(dm.date, "2024-01-02")
+        self.assertEqual(dm.revision, None)
+        self.assertEqual(dm.version, None)
+
+    def test_dependency_data_repo_is_canonical(self):
+        dm = DependencyMetadata()
+        dm.add_entry("name", "package")
+        dm.add_entry("url", "This is the canonical repo.")
+
+        self.assertEqual(dm.url, None)
+        self.assertEqual(dm.is_canonical, True)
+
+
+if __name__ == "__main__":
+    unittest.main()