diff --git a/packages/element-web-module-api/element-web-module-api.api.md b/packages/element-web-module-api/element-web-module-api.api.md
index 1e41a6da51..c86bf9cc60 100644
--- a/packages/element-web-module-api/element-web-module-api.api.md
+++ b/packages/element-web-module-api/element-web-module-api.api.md
@@ -6,6 +6,7 @@
 
 import { JSX } from 'react';
 import { ModuleApi } from '@matrix-org/react-sdk-module-api';
+import { RoomEvent } from 'matrix-js-sdk';
 import { Root } from 'react-dom/client';
 import { RuntimeModule } from '@matrix-org/react-sdk-module-api';
 
@@ -60,26 +61,42 @@ export interface ConfigApi {
     get<K extends keyof Config = never>(key?: K): Config | Config[K];
 }
 
+// @public (undocumented)
+export interface ContextMenuItem {
+    iconClassName: string;
+    label: string;
+    onClick: (e: React.MouseEvent<Element> | React.KeyboardEvent<Element> | React.FormEvent<Element>) => void | Promise<void>;
+}
+
 // @public
 export type CustomComponentProps = {
-    [CustomComponentTarget.TextualEvent]: {
-        mxEvent: any;
-        stripReply: boolean;
+    [CustomComponentTarget.TextualBody]: {
+        mxEvent: RoomEvent;
+        highlights?: string[];
+        showUrlPreview?: boolean;
+        forExport?: boolean;
+    };
+    [CustomComponentTarget.MessageContextMenu]: {
+        mxEvent: RoomEvent;
+        closeMenu: () => void;
     };
 };
 
 // @public
-export type CustomComponentRenderFunction<T extends CustomComponentTarget> = (props: CustomComponentProps[T], originalComponent: JSX.Element) => JSX.Element | null;
+export type CustomComponentRenderFunction<T extends CustomComponentTarget> = (
+props: CustomComponentProps[T],
+originalComponent: JSX.Element) => JSX.Element | null;
 
 // @public
 export interface CustomComponentsApi {
+    buildContextMenuBlock(items: ContextMenuItem[]): JSX.Element;
     register<T extends CustomComponentTarget>(target: T, renderer: CustomComponentRenderFunction<T>): void;
 }
 
 // @public
 export enum CustomComponentTarget {
-    // (undocumented)
-    TextualEvent = "TextualEvent"
+    MessageContextMenu = "MessageContextMenu",
+    TextualBody = "TextualBody"
 }
 
 // @alpha @deprecated (undocumented)
diff --git a/packages/element-web-module-api/package.json b/packages/element-web-module-api/package.json
index 9c0e0cc364..cd329b8788 100644
--- a/packages/element-web-module-api/package.json
+++ b/packages/element-web-module-api/package.json
@@ -44,13 +44,15 @@
         "vite": "^6.0.11",
         "vite-plugin-dts": "^4.5.0",
         "vitest": "^3.0.5",
-        "vitest-sonar-reporter": "^2.0.0"
+        "vitest-sonar-reporter": "^2.0.0",
+        "matrix-js-sdk": "^37.5.0"
     },
     "peerDependencies": {
         "@matrix-org/react-sdk-module-api": "*",
         "@types/react": "*",
         "@types/react-dom": "*",
         "matrix-web-i18n": "*",
+        "matrix-js-sdk": "*",
         "react": "^19"
     },
     "peerDependenciesMeta": {
diff --git a/packages/element-web-module-api/src/api/custom-components.ts b/packages/element-web-module-api/src/api/custom-components.ts
index 582a281ce1..f3cd115582 100644
--- a/packages/element-web-module-api/src/api/custom-components.ts
+++ b/packages/element-web-module-api/src/api/custom-components.ts
@@ -1,21 +1,38 @@
-import { ComponentType, JSX, MouseEventHandler, PropsWithChildren } from "react";
+import type { JSX } from "react";
+import type { RoomEvent } from "matrix-js-sdk";
 
 /**
- * Target of the renderer function.
+ * Targets in Element for custom components.
  * @public
  */
 export enum CustomComponentTarget {
     /**
-     * TODO: We should make this more descriptive.
-     * The renderer for text events in the timeline, such as "m.room.message"
+     * Component that renders "m.room.message" events in the room timeline.
      */
     TextualBody = "TextualBody",
+    /**
+     * "Options" Context menu for a timeline event.
+     * Use `buildContextMenuBlock` to build a section to be used by this component.
+     * @see buildContextMenuBlock
+     */
     MessageContextMenu = "MessageContextMenu",
 }
 
 export interface ContextMenuItem {
+    /**
+     * The human readable label for an event.
+     * TODO: Should this be i18n-d
+     */
     label: string;
+    /**
+     * The icon to use for this item.
+     * https://github.com/vector-im/riot-web/blob/efc6149a8b3362c01b93f52e76e5c4ae8cbcb65c/res/css/views/context_menus/_MessageContextMenu.pcss#L10
+     */
     iconClassName: string;
+    /**
+     * Handler for click events on the context menu item.
+     * Does NOT close the menu after execution.
+     */
     onClick: (
         e: React.MouseEvent<Element> | React.KeyboardEvent<Element> | React.FormEvent<Element>,
     ) => void | Promise<void>;
@@ -28,12 +45,12 @@ export interface ContextMenuItem {
 export type CustomComponentProps = {
     [CustomComponentTarget.TextualBody]: {
         /**
-         * The Matrix event information.
-         * TODO: Should this just use the types from matrix-js-sdk?
+         * The Matrix event for this textual body.
          */
-        mxEvent: any;
+        mxEvent: RoomEvent;
         /**
-         * Words to highlight on
+         * Words to highlight on (e.g. from search results).\
+         * May be undefined if the client does not need to highlight
          */
         highlights?: string[];
         /**
@@ -47,12 +64,11 @@ export type CustomComponentProps = {
     };
     [CustomComponentTarget.MessageContextMenu]: {
         /**
-         * The Matrix event information.
-         * TODO: Should this just use the types from matrix-js-sdk?
+         * The Matrix event which this context menu targets.
          */
-        mxEvent: any;
+        mxEvent: RoomEvent;
         /**
-         * Close the menu
+         * Function that will close the menu.
          */
         closeMenu: () => void;
     };
@@ -62,24 +78,37 @@ export type CustomComponentProps = {
  * @public
  */
 export type CustomComponentRenderFunction<T extends CustomComponentTarget> = (
+    /**
+     * Properties from the given target to be used for rendering.
+     */
     props: CustomComponentProps[T],
+    /**
+     * The original component.
+     */
     originalComponent: JSX.Element,
 ) => JSX.Element | null;
 
 /**
- * The API for creating custom components.
+ * API for inserting custom components into Element.
  * @public
  */
 export interface CustomComponentsApi {
     /**
      * Register a renderer for a component type.
-     * @param target - The target type of component
+     * The render function should either return a rendered component, or `null` if the
+     * component should not be overidden.
+     *
+     * Multiple render function may be registered for a single target, however the first
+     * non-null result will be used. If all results are null, or no registrations exist
+     * for a target then the original component is used.
+     *
+     * @param target - The target location for the component.
      * @param renderer - The render method.
      */
     register<T extends CustomComponentTarget>(target: T, renderer: CustomComponentRenderFunction<T>): void;
 
     /**
-     * Register a context menu section with a given set of items.
+     * Generate a context menu section for a given set of items.
      * @param items - A set of items to render.
      */
     buildContextMenuBlock(items: ContextMenuItem[]): JSX.Element;