Open the marked link in ChatGPT’s built-in browser
Start from your normal Valet address with __valet_webmcp=1 added to the query. Use the link maker above to avoid editing it by hand.
Three steps
Open it. Check it. Ask.
WebMCP works while the artifact is open in ChatGPT’s built-in browser. There is no separate MCP server to connect.
Sign in to Valet
Valet may move the tab to an opaque <id>.sites.valet.run address. That is expected. It gives the artifact its own browser security boundary while Valet keeps checking your access.
Ask Codex to use the page’s Site tools
Keep the tab open. Ask for the task in plain language, or list the tools first when you are checking setup.
A useful first prompt
Prove discovery before doing work.
Paste into Codex
List the Site tools available on this page. Then tell me which tool you would use for my task before calling it.
Why the marked link matters
Same artifact. Different level.
Codex currently discovers tools only in the top-level document. Valet’s normal shell keeps customer code isolated in an iframe, so direct mode changes where the artifact runs—not who may open it.
Normal Valet address
Best for ordinary viewing, comments, and the Valet shell.
WebMCP direct mode
The artifact is top-level, so Codex can discover its registered tools.
Access model
The address is visible. The content stays private.
The opaque hostname is an isolated origin, not a secret key. Knowing it does not grant access to the artifact or its tools.
- ✓Private artifacts still require Valet authentication.
- ✓Valet checks live organization membership on every request.
- ✓The WebMCP marker and session cookie change presentation only.
- ✓Tool callbacks run inside the signed-in page and use its normal permissions.
How WebMCP works
The browser is the bridge.
WebMCP turns capabilities already present in a web app into structured tools an agent can understand and invoke.
The artifact gives the browser a tool name, description, input schema, and JavaScript callback.
Codex reads the tools registered by the open top-level document.
The browser mediates the call and applies its normal safety checks.
The callback runs in the live page, with the same state and access as the person viewing it.
If it does not appear
Check the browser first.
Codex says no Site tools are available
Confirm that the tab was opened from the URL containing __valet_webmcp=1. The normal Valet address uses an iframe and its tools are not currently discoverable.
The page works in Chrome but no tools appear
Use the built-in browser in the ChatGPT desktop app. Ordinary Chrome does not make ChatGPT Site tools available. Chrome’s own WebMCP implementation remains an experimental developer feature.
The opaque address looks public
The hostname is visible by design, but it is not an access token. An unauthorized visitor is sent through Valet authentication and cannot read a private artifact.
Tools appear locally but not after publishing
Open the published artifact with direct mode and keep its tab active. Site tools belong to the page that registered them and disappear when that page closes or navigates away.