Codex Browser Adds WebMCP Support for Site Tools
CodexOpenAI brought support for WebMCP, an emerging open web standard, to the built-in browser of the Codex and ChatGPT Work desktop app. Site owners can now register tools directly in JavaScript that Codex discovers and calls on the page itself — searching a catalog, setting a dashboard's date range, or filling out a form — without the user or agent standing up a separate MCP server connection. The feature requires GPT-5.6 Sol or Terra (Luna has it disabled) and ships alongside a WebMCP Challenge for site builders, with submissions due September 4, 2026.
Key Takeaways
- WebMCP lets websites expose tools directly to Codex through a JavaScript API, removing the need to stand up and connect a separate MCP server.
- A "Site tools" indicator in the desktop app's browser address bar shows which tools are available and which ones Codex has recently used on a page.
- Codex acts on the same authenticated session as the human user, so it can work inside logged-in dashboards and internal tools without a separate credential flow.
- The feature is gated to GPT-5.6 Sol and Terra — Luna has WebMCP disabled, and it's unavailable in Enterprise/Edu workspaces at launch.
- Every tool call goes through a safety review, and website-supplied tool data is treated as untrusted content rather than as trusted instructions.
- OpenAI paired the launch with a WebMCP Challenge (deadline September 4, 2026, prizes from Shopify, Google Chrome, Netlify, Cloudflare, Vercel, Render) to seed adoption among site builders.
Sources & Mentions
2 external resources covering this update
What's New
Codex's desktop app browser now speaks WebMCP. When a user opens a WebMCP-compatible site inside the built-in browser and asks Codex for help, the agent can discover the tools that site has exposed and call them directly, rather than clicking around the page the way it previously had to. A "Site tools" indicator appears in the browser's address bar so users can see which tools are available on the current page and which ones Codex has recently used.
This is different from a traditional MCP server, which runs independently and needs to be configured as a separate connection. WebMCP tools live inside the website's own JavaScript, so there's nothing for the user to install or connect — Codex simply picks them up the moment it visits a compatible page.
How It Works
Codex operates on the same live page and authenticated session the human user already has open, which means it can act on interfaces that require a login — a dashboard, a document editor, an internal admin tool — without a separate credential flow. Developers add WebMCP support to their own sites by registering tools through the document.modelContext.registerTool() JavaScript API, describing narrow, well-scoped actions (set a date range, find a section, compare two options, leave a comment) that reuse the site's existing authentication and validation logic.
Every WebMCP tool invocation goes through a safety review before it runs, and the same confirmation policies that already govern consequential actions — purchases, deletions, permission changes — still apply. Website-supplied tool definitions and their results are treated as untrusted content by Codex, not as trusted instructions. Users can turn site tools off entirely in Settings.
Requirements and Rollout
WebMCP support requires the GPT-5.6 Sol or Terra models; GPT-5.6 Luna has the feature disabled, and it is not available in Enterprise or Edu workspaces at launch. OpenAI paired the release with a WebMCP Challenge inviting developers to build WebMCP-compatible sites, with entries due September 4, 2026 and prizes contributed by Shopify, Google Chrome, Netlify, Cloudflare, Vercel, and Render — an early signal that OpenAI wants a broad ecosystem of agent-ready websites, not just a handful of partner integrations.