diff --git a/README.md b/README.md
index 055dc31..89f930a 100644
--- a/README.md
+++ b/README.md
@@ -20,14 +20,22 @@ Either bucket can live on either track. Credits are optional metadata any module
 
 | Module | Bucket | Track | Adopted from |
 |---|---|---|---|
-| Media Library: disable infinite scroll by default | Feature | Practical | WordPress core |
-| Heading-order validation | Experiment | TBD | — |
+| Media Library: add view options | Feature | Practical | WordPress core |
 | Block Validation Framework | Experiment | Core-track | validation-api (Troy Chaplin) |
 | Core block accessibility rules | Feature | Practical | validation-api-core-blocks (Troy Chaplin) |
 | Validation settings | Feature | Practical | validation-api-settings (Troy Chaplin) |
 
 ## Block validation subsystem
 
+### Terminology
+
+Two words do a lot of work in this subsystem, so to be precise: **validation** names the mechanism, **accessibility** names the subject a particular rule set tests.
+
+- **Block Validation Framework** — the Experiment module that provides the mechanism. It is a named subsystem, so it takes title case; the other module labels are descriptive and use sentence case.
+- **Validation API** — the developer-facing interface that framework exposes: the `validation_api_register_*()` functions, the `editor.validateBlock` / `editor.validateMeta` / `editor.validateEditor` JS filters, the `validation_api_check_level` filter, and `GET /wp-validation/v1/checks`. This is why the code prefix is `validation_api_`.
+- **Validation check** — a single registered rule, whatever its subject.
+- **Core block accessibility rules** — one consumer of the framework: WCAG-oriented checks for core blocks. Accessibility is what they test; validation is how they run.
+
 Three of the first-party modules compose into a full block-editor validation subsystem:
 
 1. **Block Validation Framework** — a plugin API (`validation_api_register_block_check()`, `validation_api_register_meta_check()`, `validation_api_register_editor_check()`), an `accessibility-lab/validation` data store, real-time debounced validation, publish locking, a Validation sidebar, and REST introspection at `GET /wp-validation/v1/checks`.
diff --git a/includes/Modules/Experiments/BlockValidation/Global_Functions.php b/includes/Modules/Experiments/BlockValidation/Global_Functions.php
index 1d5d532..0390ebd 100644
--- a/includes/Modules/Experiments/BlockValidation/Global_Functions.php
+++ b/includes/Modules/Experiments/BlockValidation/Global_Functions.php
@@ -1,6 +1,6 @@
 <?php
 /**
- * Global registration functions for the block-validation framework.
+ * Global registration functions for the Block Validation Framework module.
  *
  * Third-party plugins call these on `init`. They resolve to the module's
  * Check_Registry instance held by the framework module. Defined only when
diff --git a/includes/Modules/Experiments/BlockValidation/Rest_Controller.php b/includes/Modules/Experiments/BlockValidation/Rest_Controller.php
index e3c5729..0ee8d8a 100644
--- a/includes/Modules/Experiments/BlockValidation/Rest_Controller.php
+++ b/includes/Modules/Experiments/BlockValidation/Rest_Controller.php
@@ -1,6 +1,6 @@
 <?php
 /**
- * REST introspection for the block-validation framework.
+ * REST introspection for the Block Validation Framework module.
  *
  * @package AccessibilityLab
  */
diff --git a/includes/Modules/Features/Core_Block_Validation_Rules.php b/includes/Modules/Features/Core_Block_Validation_Rules.php
index 7ede0b7..bb23b35 100644
--- a/includes/Modules/Features/Core_Block_Validation_Rules.php
+++ b/includes/Modules/Features/Core_Block_Validation_Rules.php
@@ -9,7 +9,7 @@
  * duplication check, non-descriptive alt patterns, gallery inheritance,
  * required post/page title).
  *
- * Silently no-ops if the framework module isn't active.
+ * Silently no-ops if the Block Validation Framework module isn't active.
  *
  * @package AccessibilityLab
  */
@@ -23,31 +23,61 @@
 use AccessibilityLab\Credits;
 use AccessibilityLab\Track;
 
+/**
+ * Core Block Validation Rules module.
+ *
+ * Presented to users as "Core block accessibility rules". Accessibility is the
+ * subject these rules test; validation is the mechanism they run on — the Block
+ * Validation Framework is the general mechanism, and this module is one
+ * consumer of it.
+ *
+ * The class name and the `core_block_validation_rules` id are deliberately left
+ * as they are: the id is persisted in the `accessibility_lab_settings` option,
+ * so renaming it would reset the module's toggle on existing installs.
+ */
 final class Core_Block_Validation_Rules extends Abstract_Module {
 
 	private const NS = 'accessibility-lab-core-blocks';
 
+	/**
+	 * Returns the ID for the core block accessibility rules module.
+	 */
 	public function id(): string {
 		return 'core_block_validation_rules';
 	}
 
+	/**
+	 * Returns the bucket for the core block accessibility rules module.
+	 */
 	public function bucket(): string {
 		return Bucket::FEATURE;
 	}
 
+	/**
+	 * Returns the track for the core block accessibility rules module.
+	 */
 	public function track(): string {
 		return Track::PRACTICAL;
 	}
 
+	/**
+	 * Returns the name for the core block accessibility rules module.
+	 */
 	public function name(): string {
 		return __( 'Core block accessibility rules', 'accessibility-lab' );
 	}
 
+	/**
+	 * Returns the description for the core block accessibility rules module.
+	 */
 	public function description(): string {
 		return __( 'WCAG-oriented validation checks for the image, button, table, heading, and gallery core blocks, plus required post/page titles. Requires the Block Validation Framework module.', 'accessibility-lab' );
 	}
 
-	public function credits(): ?Credits {
+	/**
+	 * Returns the credits for the core block accessibility rules module.
+	 */
+	public function credits(): Credits {
 		return new Credits(
 			author: 'Troy Chaplin',
 			source_plugin_slug: 'validation-api-core-blocks',
@@ -56,11 +86,17 @@ public function credits(): ?Credits {
 		);
 	}
 
+	/**
+	 * Boots the core block accessibility rules module.
+	 */
 	public function boot(): void {
 		add_action( 'init', array( $this, 'register_checks' ) );
 		add_action( 'enqueue_block_editor_assets', array( $this, 'enqueue_editor_assets' ), 20 );
 	}
 
+	/**
+	 * Enqueues editor assets for the core block accessibility rules.
+	 */
 	public function enqueue_editor_assets(): void {
 		$asset_file = ACCESSIBILITY_LAB_DIR . '/build/core-block-rules.asset.php';
 		if ( ! file_exists( $asset_file ) ) {
@@ -89,6 +125,9 @@ public function enqueue_editor_assets(): void {
 		);
 	}
 
+	/**
+	 * Registers all core block accessibility checks.
+	 */
 	public function register_checks(): void {
 		if ( ! function_exists( 'validation_api_register_block_check' ) ) {
 			return;
@@ -108,6 +147,9 @@ public function register_checks(): void {
 		$this->register_editor_checks();
 	}
 
+	/**
+	 * Registers image block accessibility checks.
+	 */
 	private function register_image_checks(): void {
 		validation_api_register_block_check(
 			'core/image',
@@ -181,6 +223,9 @@ private function register_image_checks(): void {
 		}
 	}
 
+	/**
+	 * Registers button block accessibility checks.
+	 */
 	private function register_button_checks(): void {
 		validation_api_register_block_check(
 			'core/button',
@@ -208,6 +253,9 @@ private function register_button_checks(): void {
 		);
 	}
 
+	/**
+	 * Registers table block accessibility checks.
+	 */
 	private function register_table_checks(): void {
 		validation_api_register_block_check(
 			'core/table',
@@ -223,6 +271,9 @@ private function register_table_checks(): void {
 		);
 	}
 
+	/**
+	 * Registers heading block accessibility checks.
+	 */
 	private function register_heading_checks(): void {
 		validation_api_register_block_check(
 			'core/heading',
@@ -238,6 +289,9 @@ private function register_heading_checks(): void {
 		);
 	}
 
+	/**
+	 * Registers editor accessibility checks.
+	 */
 	private function register_editor_checks(): void {
 		foreach ( array( 'post', 'page' ) as $post_type ) {
 			validation_api_register_editor_check(
diff --git a/src/editor/core-block-rules/button.ts b/src/editor/core-block-rules/button.ts
index 62120ae..3a28a80 100644
--- a/src/editor/core-block-rules/button.ts
+++ b/src/editor/core-block-rules/button.ts
@@ -12,6 +12,8 @@ function stripHtml( html: string ): string {
  * Minimal URL sanity check. A full Public Suffix List (PSL) integration is
  * planned as a follow-up — for now we accept any parseable http(s), mailto:,
  * tel:, or root-relative URL.
+ *
+ * @param raw URL as entered in the block's link control.
  */
 function isPlausibleUrl( raw: string ): boolean {
 	const value = raw.trim();
@@ -38,7 +40,12 @@ function isPlausibleUrl( raw: string ): boolean {
 addFilter(
 	'editor.validateBlock',
 	'accessibility-lab-core-blocks/button',
-	( isValid: boolean, blockType: string, attributes: Record< string, unknown >, checkName: string ) => {
+	(
+		isValid: boolean,
+		blockType: string,
+		attributes: Record< string, unknown >,
+		checkName: string
+	) => {
 		if ( blockType !== 'core/button' ) {
 			return isValid;
 		}
diff --git a/src/editor/core-block-rules/gallery.ts b/src/editor/core-block-rules/gallery.ts
index 6e2f800..27a0289 100644
--- a/src/editor/core-block-rules/gallery.ts
+++ b/src/editor/core-block-rules/gallery.ts
@@ -3,8 +3,7 @@
  * by iterating the gallery's inner image blocks.
  */
 
-import { addFilter } from '@wordpress/hooks';
-import { applyFilters } from '@wordpress/hooks';
+import { addFilter, applyFilters } from '@wordpress/hooks';
 
 type GalleryAttributes = {
 	images?: Array< Record< string, unknown > >;
@@ -20,7 +19,13 @@ const CHECK_MAP: Record< string, string > = {
 addFilter(
 	'editor.validateBlock',
 	'accessibility-lab-core-blocks/gallery',
-	( isValid: boolean, blockType: string, attributes: GalleryAttributes, checkName: string, rule: unknown ) => {
+	(
+		isValid: boolean,
+		blockType: string,
+		attributes: GalleryAttributes,
+		checkName: string,
+		rule: unknown
+	) => {
 		if ( blockType !== 'core/gallery' ) {
 			return isValid;
 		}
diff --git a/src/editor/core-block-rules/heading.ts b/src/editor/core-block-rules/heading.ts
index e5c58fd..cb8f7ab 100644
--- a/src/editor/core-block-rules/heading.ts
+++ b/src/editor/core-block-rules/heading.ts
@@ -35,14 +35,25 @@ function flattenBlocks( blocks: Block[] ): Block[] {
 addFilter(
 	'editor.validateBlock',
 	'accessibility-lab-core-blocks/heading',
-	( isValid: boolean, blockType: string, attributes: { level?: number }, checkName: string, _rule: unknown, /* extra */ ) => {
-		if ( blockType !== 'core/heading' || checkName !== 'check_heading_rank' ) {
+	(
+		isValid: boolean,
+		blockType: string,
+		attributes: { level?: number },
+		checkName: string
+	) => {
+		if (
+			blockType !== 'core/heading' ||
+			checkName !== 'check_heading_rank'
+		) {
 			return isValid;
 		}
-		const level = Number( attributes.level ?? 2 );
 		// Locate previous heading in document order.
 		const blocks = flattenBlocks(
-			( select( blockEditorStore ) as unknown as { getBlocks: () => Block[] } ).getBlocks()
+			(
+				select( blockEditorStore ) as unknown as {
+					getBlocks: () => Block[];
+				}
+			 ).getBlocks()
 		);
 		const headings = blocks.filter( ( b ) => b.name === 'core/heading' );
 		// We don't have clientId in the filter args; approximate by finding the
@@ -52,7 +63,10 @@ addFilter(
 		if ( headings.length === 0 ) {
 			return true;
 		}
-		const firstHeadingLevel = Number( headings[ 0 ].attributes?.level ?? 2 );
+		const level = Number( attributes.level ?? 2 );
+		const firstHeadingLevel = Number(
+			headings[ 0 ].attributes?.level ?? 2
+		);
 		if ( level === firstHeadingLevel ) {
 			return firstHeadingLevel <= 2;
 		}
diff --git a/src/editor/core-block-rules/image.ts b/src/editor/core-block-rules/image.ts
index bd401f2..5a4c424 100644
--- a/src/editor/core-block-rules/image.ts
+++ b/src/editor/core-block-rules/image.ts
@@ -15,21 +15,23 @@ function stripHtml( html: string ): string {
 addFilter(
 	'editor.validateBlock',
 	'accessibility-lab-core-blocks/image',
-	( isValid: boolean, blockType: string, attributes: Record< string, unknown >, checkName: string ) => {
+	(
+		isValid: boolean,
+		blockType: string,
+		attributes: Record< string, unknown >,
+		checkName: string
+	) => {
 		if ( blockType !== 'core/image' ) {
 			return isValid;
 		}
 		const alt = String( attributes.alt ?? '' ).trim();
-		const caption = stripHtml( String( attributes.caption ?? '' ) );
 		const isDecorative = Boolean( attributes.isDecorative );
 		const hasImage = Boolean( attributes.url || attributes.id );
 
 		switch ( checkName ) {
 			case 'check_image_alt_text':
-				if ( ! hasImage || isDecorative ) {
-					return true;
-				}
-				return alt.length > 0;
+				// Passes with no image yet, a decorative image, or non-empty alt text.
+				return ! hasImage || isDecorative || alt.length > 0;
 
 			case 'check_image_alt_text_length':
 				if ( ! alt ) {
@@ -37,11 +39,13 @@ addFilter(
 				}
 				return alt.length <= 125;
 
-			case 'check_image_alt_caption_match':
+			case 'check_image_alt_caption_match': {
+				const caption = stripHtml( String( attributes.caption ?? '' ) );
 				if ( ! alt || ! caption ) {
 					return true;
 				}
 				return alt.toLowerCase() !== caption.toLowerCase();
+			}
 
 			case 'check_image_alt_text_patterns':
 				if ( ! alt || isDecorative ) {
diff --git a/src/editor/core-block-rules/post-title.ts b/src/editor/core-block-rules/post-title.ts
index 7e4d280..3cf337a 100644
--- a/src/editor/core-block-rules/post-title.ts
+++ b/src/editor/core-block-rules/post-title.ts
@@ -10,13 +10,16 @@ addFilter(
 	'editor.validateEditor',
 	'accessibility-lab-core-blocks/post-title',
 	( isValid: boolean, checkName: string ) => {
-		if ( checkName !== 'post_title_required_post' && checkName !== 'post_title_required_page' ) {
+		if (
+			checkName !== 'post_title_required_post' &&
+			checkName !== 'post_title_required_page'
+		) {
 			return isValid;
 		}
-		const currentPost = ( select( editorStore ) as unknown as {
+		const currentPost = select( editorStore ) as unknown as {
 			getCurrentPost: () => { type?: string };
 			getEditedPostAttribute: ( name: string ) => unknown;
-		} );
+		};
 		const postType = currentPost.getCurrentPost().type;
 		if ( checkName === 'post_title_required_post' && postType !== 'post' ) {
 			return true;
@@ -24,7 +27,9 @@ addFilter(
 		if ( checkName === 'post_title_required_page' && postType !== 'page' ) {
 			return true;
 		}
-		const title = String( currentPost.getEditedPostAttribute( 'title' ) ?? '' ).trim();
+		const title = String(
+			currentPost.getEditedPostAttribute( 'title' ) ?? ''
+		).trim();
 		return title.length > 0;
 	}
 );
diff --git a/src/editor/core-block-rules/table.ts b/src/editor/core-block-rules/table.ts
index 9801cc5..60478c8 100644
--- a/src/editor/core-block-rules/table.ts
+++ b/src/editor/core-block-rules/table.ts
@@ -15,7 +15,12 @@ type TableAttributes = {
 addFilter(
 	'editor.validateBlock',
 	'accessibility-lab-core-blocks/table',
-	( isValid: boolean, blockType: string, attributes: TableAttributes, checkName: string ) => {
+	(
+		isValid: boolean,
+		blockType: string,
+		attributes: TableAttributes,
+		checkName: string
+	) => {
 		if ( blockType !== 'core/table' ) {
 			return isValid;
 		}
@@ -24,7 +29,8 @@ addFilter(
 			return isValid;
 		}
 
-		const hasHead = Array.isArray( attributes.head ) && attributes.head.length > 0;
+		const hasHead =
+			Array.isArray( attributes.head ) && attributes.head.length > 0;
 		if ( hasHead ) {
 			return true;
 		}