Essential WebMCP Site Tools for ChatGPT Desktop 2026

The built-in browser in the ChatGPT desktop app and on ChatGPT Sites can now discover WebMCP tools that a compatible page publishes. OpenAI calls this feature site tools. ChatGPT Work and Codex can invoke those named functions instead of guessing click targets.

📑Table of Contents

1. WebMCP replaces click guessing with page-published tools
2. How to use site tools in ChatGPT desktop, and what blocks them
3. Make your site or ChatGPT Sites agent-ready
4. WebMCP Challenge dates, prizes, and submission rules
5. Frequently asked questions
6. Wrap-up

What has to be true for site tools

The usable window is narrow. All four of the following conditions must be true at once.

• GPT-5.6 Sol or Terra
• a current desktop app
• the in-app browser
• a page that actually registers tools

Luna has WebMCP disabled. Enterprise and Edu workspaces are out. ChatGPT in Chrome does not run site tools. As of the 25 August 2026 announcement, the primary record is the OpenAI Developers thread plus OpenAI Learn, not a long-form product blog.

---

What this article covers

---

WebMCP replaces click guessing with page-published tools

Tools on the live page

WebMCP lets a page register JavaScript functions as tools by supplying a name, a description, and a structured input schema. The person and the agent share the live page and the signed-in session. Codex and ChatGPT Work then call those functions instead of scraping the DOM.

---

How WebMCP differs from MCP

MCP still connects an AI app to a local or remote server and can work with no webpage open. WebMCP does not add a per-site connector. OpenAI Learn treats that as the product distinction. One site can expose both.

---

Draft names, annotations, and lifetime

The W3C Web Machine Learning Community Group draft sets these constraints.

• Tool names are 1–128 characters
• Only ASCII alphanumerics plus _, -, and .
• Annotations include readOnlyHint and untrustedContentHint (both default false)
• Closing the page drops that page’s tools

The draft is not a W3C Standard and is not on the Standards Track, so the API can still change.

---

How the three paths compare

Path	Where it runs	Connection	Best fit
Ordinary browser use	Open tab	None	Clicks and typing; brittle when layout changes
MCP	Local or remote server	Separate connector	API-like work without opening the page
WebMCP / site tools	Open page plus signed-in session	No extra connection	Human and agent share the same screen

Source: OpenAI Learn (site tools / WebMCP), W3C WebMCP draft (as of August 2026)

---

What execute should call

Call existing application logic from execute. You do not need a hidden agent-only API first. Tool definitions and return values are untrusted. A read-only name is not proof.

---

How to use site tools in ChatGPT desktop, and what blocks them

Use the ChatGPT desktop in-app browser, not Chrome. The Help Center lists six steps.

The official six steps

1. Open the built-in browser from the desktop toolbar.
2. Visit the site and sign in on that site if needed. Chrome login does not carry over.
3. Check the address-bar arrow for available tools (gray = available, blue = running).
4. Tell ChatGPT the task.
5. Review any site-access prompt.
6. Check the result on the page or in the conversation. Recently used opens Sources.

---

Model, workspace, and Chrome limits

The limits are:

• Switch the model to GPT-5.6 Sol or Terra. Luna has WebMCP disabled
• Enterprise and Edu workspaces cannot use site tools
• No separate connector is required, and the surface is in-app-browser only
• Embedded-content tools are unsupported. Tools stay bound to the providing page
• Settings > Browser > Permissions can turn Enable site tools off

Developers still have a Chrome test path. Netlify documents chrome://flags/#enable-webmcp-testing. WebProNews reported a Chrome 149 origin trial. That is not the path for ordinary ChatGPT desktop use.

---

Confirmation prompts and the first three checks

ChatGPT asks for confirmation before these actions.

• purchases
• deletions
• permission changes
• sending messages
• sharing personal data

Enter passwords on the website, never in the conversation. The Help Center still warns about exfiltration and prompt injection. A per-invocation safety review does not prove the site is trustworthy.

Check these three facts first.

• Sol or Terra
• a current desktop build
• whether the page actually exposes tools

If the arrow stays dark, the cause is one of the following: model limits, an unsupported workspace, using Chrome instead of the in-app browser, a page with no tools, or tools trapped in an embed.

---

Make your site or ChatGPT Sites agent-ready

The official minimum is document.modelContext.registerTool. Feature-detect, then pass an existing function to execute. OpenAI’s thread says you can update the desktop app and ask Codex to build a compatible site and deploy it to Sites.

Minimal registerTool steps

1. Confirm typeof document.modelContext?.registerTool === "function".
2. Register name, description, inputSchema, and execute. Set annotations.readOnlyHint: true for reads.
3. Keep inputs narrow, describe side effects, and return values a human can verify.
4. Reuse the site’s existing auth, authorization, and validation.
5. Keep the ordinary UI for browsers that do not speak WebMCP.

if (typeof document.modelContext?.registerTool === "function") {
  document.modelContext.registerTool({
    name: "search_docs",
    description: "Search public docs by keyword",
    inputSchema: {
      type: "object",
      properties: { query: { type: "string" } },
      required: ["query"]
    },
    annotations: { readOnlyHint: true },
    execute: async ({ query }) => existingSearch(query)
  });
}

---

document versus navigator

Netlify’s Challenge post shows navigator.modelContext.registerTool. Current OpenAI Learn examples use document.modelContext. Detect both.

Docs examples include:

• search_openai_docs
• lookup_page
• lookup_context
• navigate_to_page
• generate_custom_guide

---

Headless versus co-browse

Nekuda splits the design into headless mode, where the agent proceeds on the customer’s behalf, and co-browse mode, where the person and agent share one live page. Publishing a tool is not a finished customer journey. Ship search and lookup first. Keep purchase and send flows behind confirmation.

WebProNews (26 August 2026) reported Shopify enabling tools on Liquid storefronts and Cloudflare adding a dashboard toggle. Treat those as industry context, not a reason to bypass your own authorization boundary.

---

WebMCP Challenge dates, prizes, and submission rules

The contest runs ten days. Cash goes to the top 10. Treat 3 September, 1 p.m. PT on the official page as the deadline. Do not use Netlify’s 5 p.m. PT close. Aim four hours earlier.

Official versus Netlify clocks

Item	Official openai.com / Devpost	Netlify blog
Open	25 August, 12 p.m. PT (official page)	25 August, 11 a.m. PT
Kickoff livestream	—	25 August, 3 p.m. PT
Office hours	—	31 August, 11 a.m. PT
Submission deadline	3 September, 1 p.m. PT	3 September, 5 p.m. PT
Winners	23 September (may slip with volume)	23 September

Source: OpenAI WebMCP Challenge, Netlify blog, Quasa recap (as of August 2026)

---

Prizes and submission pieces

Each of the top 10 receives $3,000 cash from OpenAI. Quasa adds $500 Netlify cash for $3,500 × 10 = $35,000. The official page also lists:

• one year of ChatGPT Pro
• a Codex Micro
• extra prizes from Shopify, Chrome, Netlify, Cloudflare, Vercel, and Render

Netlify separately advertises 3 million credits and a $5,000 prize pool.

Submit all of the following.

• a hosted working app
• a written description
• a public open-source repository
• a demo video with audio

Judging uses the ChatGPT in-app browser or Chrome with WebMCP enabled. If you enter, lock the live app, public repo, and demo to the official 1 p.m. PT cutoff.

---

Frequently asked questions

Q. How is WebMCP different from MCP?

A. MCP connects to a server without opening a page. WebMCP registers tools on the open page and needs no extra connector. A site can offer both. Source: OpenAI Learn

Q. Why don’t site tools appear in my ChatGPT?

A. Split in this order:

• Luna
• Enterprise/Edu
• an outdated desktop app
• ChatGPT in Chrome
• a page with no tools
• tools inside an embed

Source: OpenAI Help Center

Deadline, passwords, and spec stability

Q. Can I use Netlify’s 5 p.m. PT Challenge deadline?

A. No. The official page and Devpost use 3 September, 1 p.m. PT. Use the earlier time. Source: OpenAI WebMCP Challenge

Q. Can I paste a password into ChatGPT?

A. No. Type it on the website. Source: OpenAI Help Center

Q. Is the spec stable?

A. It is an experimental Community Group draft, not a Standard. The navigator versus document registration split remains. Source: W3C WebMCP draft

---

Wrap-up

The shift is from click guessing to calling tools a site publishes. The working conditions are a current ChatGPT desktop app, GPT-5.6 Sol or Terra, the in-app browser, and a page that exposes tools. Luna, Enterprise, Edu, and ChatGPT-in-Chrome are out.

Do this next

• ✓ Update ChatGPT desktop
• ✓ Switch to GPT-5.6 Sol or Terra (Luna / Enterprise / Edu are excluded)
• ✓ Open a compatible site in the in-app browser and check the address-bar site tools
• ✓ On your own site, register one existing action with document.modelContext.registerTool and leave confirmation on sensitive actions
• ✓ If you enter the Challenge, ship a live app, public repo, and demo video by 3 September, 1 p.m. PT

Rollout coverage, Chrome general availability, draft API drift, and the Netlify versus official clock remain open. Prefer the official page over secondary write-ups for the deadline and model limits.

Related articles:

• 13644
• 13631