Testing with the fake agent

No mainstream agent calls WebMCP yet, so @webmcpui/core/testing ships a fake host that lets you exercise exposure end to end. It installs a stub navigator.modelContext, records the tools your elements register, and lets you invoke them exactly as an agent would.

import { installFakeAgent } from '@webmcpui/core/testing';

const agent = installFakeAgent();

// ... connect a <wmcp-input name="email" expose> to the DOM ...

const result = await agent.call('fill_email', { value: 'ada@webmcpui.com' });
// the live element is now filled, validated, and has fired input/change

agent.restore(); // remove the stub

Order matters. Install the fake agent before the element connects — controls register their tool in connectedCallback, so the host must already be present.

The handle

installFakeAgent() returns:

This is exactly what powers the live demo on the homepage — the same fake host, driving real elements.