Use WebMCP tools in a browser agent

Pages on openagents.com hand their tools to the browser's agent through WebMCP. A browser agent can read the docs, list the models, and start a chat without reading the page's layout.

How the page offers them

Each page loads one script:

<script src="/static/webmcp.js" defer></script>

It looks for document.modelContext (or navigator.modelContext) and calls registerTool once for each tool. In a browser with no WebMCP, it does nothing.

The tools

Tool	Input	What it does
list_docs	{}	Lists every page with its name and summary
search_docs	{"query": "...", "limit": 5} (query required, limit 1 to 20)	Searches the docs
read_doc	{"name": "agents/start-here"}	Reads one page as Markdown
list_models	{}	Lists the API's models and their prices
start_chat	{"message": "..."}	Sends a message from the page's chat box

The first four only read. They call our docs MCP server (POST https://openagents.com/mcp/docs) and return its result object. start_chat is offered only on a page with a chat box, such as openagents.com: it fills the box, sends it, and returns Sent.; the answer shows on the page.

Step 1: list what the page offers

In a browser with WebMCP, ask the page's model context for its tools. From the browser's console, the same tools can be checked by name:

const context = document.modelContext || navigator.modelContext;
console.log(Boolean(context && context.registerTool));

Step 2: call a tool

Your browser agent calls a tool by name with its input. For example, to read the start page:

{"name": "read_doc", "arguments": {"name": "agents/start-here"}}

The result is the MCP result shape:

{"content": [{"type": "text", "text": "# For agents: start here\n..."}], "isError": false}

Step 3: start a chat

On openagents.com, logged in:

{"name": "start_chat", "arguments": {"message": "I need a summary of my open pull requests."}}

The tool returns Sent. once the message is sent. Read the answer from the page.

Without WebMCP

The same read tools are on the docs MCP server, which any agent can call over HTTP. See Connect to our MCP servers.