CLIENT GUIDE · SNAPSHOT 2026-08-31

Use Site tools in ChatGPT.

ChatGPT calls WebMCP integrations Site tools. Treat the browser's own Available site tools list as ground truth for the page that is open right now.

PAGE-BOUND, MODEL-GATED

Requirements at this snapshot

Website: the page registers WebMCP from a secure context. Use HTTPS in production or a trustworthy loopback origin in development.
ChatGPT: update the desktop app, then open the website in its built-in browser.
Model: official OpenAI documentation checked 2026-08-31 lists GPT-5.6 Sol and GPT-5.6 Terra. GPT-5.6 Luna currently has WebMCP disabled.
Workspace: the same official page says Site tools are unavailable in Enterprise and Edu; availability can also depend on rollout.
Client API: ChatGPT currently discovers imperative JavaScript tools in the top-level page. Declarative API form tools and tools registered inside iframes are not available as Site tools.

Inspect what the page registered

Keep the target page open in ChatGPT's built-in browser.
Select Site tools in the browser address bar.
Open Available site tools and inspect the individual names.
After a call, use Recently used when available to review the source and invocation.

If the expected tool is absent here, do not start by rewriting its schema. Check the model/workspace, page lifetime and secure registration first.

Troubleshoot in this order

Symptom	Check	Meaning
No Site tools control	Desktop-app version, selected model, workspace and rollout.	The client surface may be unavailable before the site is involved.
Control exists, expected tool absent	Available site tools while the exact page is open; then top-level imperative registration and secure context.	The page did not register it in the current document, registration failed, or it uses a declarative form or iframe that this client does not discover.
Tool worked, then vanished	Did the browser close, navigate, reload or replace the page between turns?	Tools belong to their page; page teardown ends that registration.
Assistant uses ordinary browser interaction	Confirm Sol/Terra plus Work or Codex and inspect Available site tools directly.	Fallback browser behavior can look like a broken integration.
Tool call is held or asks for confirmation	Review the requested action and client safety result.	Every invocation receives a client-side safety review; normal confirmation policy still applies.

Chrome proof is a separate layer

webmcpify verifies implementation behavior in current headed Chrome. Use the recorded verification origin and a dedicated writable profile:

WEBMCP_BASE_URL=https://your-secure-test-origin.example \
WEBMCP_PROFILE_DIR=/tmp/your-dedicated-webmcp-profile \
npx playwright test .webmcpify/webmcp.spec.ts

The first page probe is:

({
  secure: window.isSecureContext,
  modelContext: typeof document.modelContext
})

A green Chrome harness proves registration and execution for the tools that harness exercises in that Chrome environment. It does not prove that a particular ChatGPT account exposes the same subset as Site tools; test that client separately.

FAQ

Why does webmcpify not call this “WebMCP” in ChatGPT instructions?

Because the client label is Site tools. WebMCP is the underlying web API; Available site tools is the control a ChatGPT user can actually inspect.

Can the tools survive after I leave the page?

No compatibility promise says they can. Official OpenAI documentation states that closing or navigating away can make page-owned tools unavailable.

Does ChatGPT run a safety check?

Yes. The official guide says each built-in-browser invocation receives a safety review, and ordinary access and confirmation rules continue to apply.

Does every tool that works in Chrome appear as a Site tool?

No. As checked 2026-08-31, ChatGPT's built-in browser supports imperative tools registered in the top-level page, but not declarative form tools or registrations inside iframes. Regular browser interaction may still operate those forms.

What about plain Chat or a Work workspace?

A single session on 2026-08-26/27 observed plain Chat handing the task to Work mode and one Work workspace offering Site tools. That is a dated account/UI observation, not a published availability guarantee. Verify the exact account.

Sources and date boundary

OpenAI: Site tools, checked 2026-08-31 for naming, model/workspace availability, supported API subset, controls, page lifetime and safety review.
WebMCP draft, dated 2026-08-26, for the secure-context Document API.
Chrome WebMCP documentation for origin-trial and local verification behavior.

Re-check these pages before copying model names or workspace claims into another public surface.