Vercel's browser agent can now write its own tools

Vercel released version 0.36.0 of agent-browser on September 1. It turns on WebMCP discovery by default for any locally managed Chrome instance, per the release notes.

The agent can now find and call tools that the current page exposes. That's on by default for every local session, unless someone opts out with --no-webmcp.

The release also adds frame-aware selection, detached results, cancellation, and bounded metadata handling for tool calls.

It also ships a WebMCP generation skill. The skill helps an agent expose an existing page workflow as a validated tool, with safety constraints and a fallback path recorded. That's new. Before this, every WebMCP tool an agent could call had to be hand-built by whoever owned the site. Now the agent browsing the page can write the tool itself, and other agents can reuse it later.

The release notes don't say how the generated safety constraints get checked before a tool ships. They also don't say whether a human reviews one before other agents start calling it. That leaves site owners with a new kind of surface to audit. It's a tool generated by a process they didn't write and can't easily inspect line by line.