@context-action/webmcp

Browser adapter for exposing an explicit Context-Action tool scope through the experimental WebMCP imperative API. It does not create a second registry: ToolManagementInterface remains the authorization, validation, approval, and durable-execution boundary.

import { createWebMCPToolScope } from '@context-action/webmcp';

const scope = await createWebMCPToolScope(registry, {
  sessionId: 'shopping-page:42',
  toolNames: ['searchCatalog', 'addToCart'],
  exposedTo: ['https://agent.example'],
});

// Call on page teardown. WebMCP unregisters the scoped tools via AbortSignal.
scope.dispose();

For React, import useWebMCPToolScope from the experimental @context-action/react/webmcp subpath and pass a memoized options object; the hook unregisters the scope on unmount.

Each scope creates unique correlation IDs for canonical calls. WebMCP does not provide a stable native retry identity, so idempotency is disabled by default; pass getIdempotencyKey only with a domain-owned retry key. Use interaction for canonical policy-gated approval: it runs only after argument validation and a policy ask decision. afterExecute is a detached post-execution notification, not an authorization boundary. Select currentWebMCPProfile by default or import @context-action/webmcp/profiles/chrome-legacy for Chrome's older registration shape. errorMode defaults to structured; use throw when the host requires rejected browser callbacks.

The adapter is safe to import during SSR and in unsupported browsers: it returns { supported: false, activeTools: [] } when document.modelContext is unavailable. It only exposes the requested toolNames; omitting the list does not publish the entire registry.

WebMCP itself requires a visible browsing context, origin isolation, and the browser tools Permissions Policy. Cross-origin exposure must be explicitly listed through exposedTo; this adapter accepts HTTPS origins and local HTTP origins only for local development.