webmcp

# WebMCP — Discover and Use Website Tools

## What is WebMCP

WebMCP is a browser API that lets websites expose JavaScript functions as structured tools for AI agents. Pages register tools via `window.navigator.modelContext`, each with a name, description, JSON Schema input, and an `execute` callback. Think of it as an MCP server running inside the web page itself.

Spec: https://github.com/webmachinelearning/webmcp

## Detecting WebMCP Support

Before interacting with tools, check whether the current page supports WebMCP:

```js
const supported = "modelContext" in window.navigator;
```

If `false`, the page does not expose WebMCP tools — fall back to DOM interaction or actuation.

## Discovering Available Tools

Tools are registered by the page via `provideContext()` or `registerTool()`. The browser mediates access. To list available tools from an agent's perspective, evaluate:

```js
// Browser-specific — the exact discovery API depends on the agent runtime.
// Typically the browser exposes registered tools to connected agents automatically.
// From page-script perspective, tools are registered like this:
window.navigator.modelContext.provideContext({
  tools: [
    {
      name: "tool-name",
      description: "What this tool does",
      inputSchema: { type: "object", properties: { /* ... */ }, required: [] },
      execute: (params, agent) => { /* ... */ }
    }
  ]
});
```

Key points:
- Each tool has `name`, `description`, `inputSchema` (JSON Schema), and `execute`.
- `provideContext()` replaces all previously registered tools (useful for SPA state changes).
- `registerTool()` / `unregisterTool()` add/remove individual tools without resetting.
- Tools may change as the user navigates or as SPA state updates — re-check after page transitions.

## Tool Schema Format

Tool input schemas follow JSON Schema (aligned with MCP SDK and Prompt API tool use):

```js
{
  name: "add-stamp",
  description: "Add a new stamp to the collection",
  inputSchema: {
    type: "o...