agenticweb.wiki

WebMCP

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This page is about WebMCP, the browser JavaScript API drafted in the W3C Web Machine Learning Community Group [1]. Two older open-source GitHub projects share the name: MiguelsPizza/WebMCP (created 2025-06-13), described as "Bringing the power of MCP to the web" [11], and jasonjmcghee/WebMCP (created 2025-03-04), which describes itself as an "Early WebMCP proposal / implementation - since evolved and worked on by much more capable folks that develop the web" [12]. The group’s chair credited Alex Nahas and Jason McGhee with early WebMCP prototypes and pointed to both repositories [13]. For the server-side protocol WebMCP borrows from, see Model Context Protocol.

Overview

WebMCP is a proposed browser API that lets a web page hand AI agents a set of named tools: JavaScript functions with descriptions and input schemas that run inside the page the user already has open [1][2]. The spec describes such pages as Model Context Protocol servers whose tools run in client-side script rather than on a backend [1]. It began in August 2025 as a joint Microsoft and Google explainer in the W3C Web Machine Learning Community Group, and its entry point has since moved twice, from window.agent to navigator.modelContext to document.modelContext [3][4][6][7]. Chrome and Edge run origin trials, Mozilla is neutral and WebKit opposes it [16][19][22][23].

Who uses it

Each site below was fetched on 2026-10-28 with its same-origin scripts, and one of them contained a registerTool() call on the WebMCP modelContext object. The page returned HTTP 200 with no redirect. This shows the site ships WebMCP code; it does not show which browsers expose the tools to agents. Google, Microsoft and Meta demos and agenticweb.wiki are not listed.

Who reads it

No OpenAI statement found as of 2026-10-28 confirming ChatGPT Desktop support.

Recent coverage

See also

References

  1. Web Machine Learning Community Group, WebMCP, Draft Community Group Report, 27 October 2026: "The WebMCP API enables web applications to provide JavaScript-based tools to AI agents." "This specification was published by the Web Machine Learning Community Group. It is not a W3C Standard nor is it on the W3C Standards Track." "Web pages that use WebMCP can be thought of as Model Context Protocol [MCP] servers that implement tools in client-side script instead of on the backend." "Draft Community Group Report, 27 October 2026" "Editors: Brandon Walderman (Microsoft) Khushal Sagar (Google) Dominic Farolino (Google) Samuel Dallstream (Microsoft)" "Also many thanks to Alex Nahas and Jason McGhee for sharing early implementation experience." — https://webmachinelearning.github.io/webmcp/
  2. webmachinelearning/webmcp, README.md (explainer, main branch; GitHub metadata shows the repository was created 2025-08-05), checked 2026-10-28 (text checked at the raw.githubusercontent.com copy): "WebMCP lets developers expose web application functionality as "tools"—JavaScript functions with natural language descriptions and structured schemas, designed for AI agent ingestion." "WebMCP is currently focused on the imperative `document.modelContext.registerTool()` API described above, which is what the specification defines." "but it is not part of the specification at this time." — https://github.com/webmachinelearning/webmcp
  3. Brandon Walderman, Leo Lee, Andrew Nolan (Microsoft), David Bokan, Khushal Sagar, Hannah Van Opstal (Google), WebMCP explainer README as of commit 7edc0e18 (2025-08-25): "First published August 13, 2025" — https://github.com/webmachinelearning/webmcp/blob/7edc0e1818636182e352b3b15d9203a29b18319b/README.md
  4. webmachinelearning/webmcp, docs/proposal.md as of commit 7edc0e18 (2025-08-25): "The `window.agent` interface is introduced to represent an abstract AI agent that is connected to the page and uses the page’s context." — https://github.com/webmachinelearning/webmcp/blob/7edc0e1818636182e352b3b15d9203a29b18319b/docs/proposal.md
  5. webmachinelearning/webmcp, commit 58b2d5e4, 2025-08-13 (pull request #3; text checked through the GitHub API): "Merge Script Tools API and WebMCP explainers [Part I]" — https://github.com/webmachinelearning/webmcp/commit/58b2d5e4e20be9627c55ec61d1bbb5d9760e132e
  6. webmachinelearning/webmcp, commit 41dd8292, 2026-02-19 (text checked through the GitHub API): "Initialize a Navigator’s modelContext member" — https://github.com/webmachinelearning/webmcp/commit/41dd8292ac19db6a43ea58aefc8fcb4662742411
  7. webmachinelearning/webmcp, commit c7b5c702, 2026-05-27 (text checked through the GitHub API): "Move the `modelContext` getter to `Document` (#184)" — https://github.com/webmachinelearning/webmcp/commit/c7b5c7023f6e6a1c7a2495946136eb19b3109ae6
  8. Chromium, commit 4a9fee9e, 2026-07-09 (text checked through the GitHub API): "WebMCP: Remove navigator.modelContext" "navigator.modelContext in favor of document.modelContext." — https://github.com/chromium/chromium/commit/4a9fee9eafcabd675c7245cc1b0acc1ca5f17d99
  9. webmachinelearning/webmcp, commit 14ae813c, 2026-10-08 (text checked through the GitHub API): "Remove declarative API from the spec for now (#338)" — https://github.com/webmachinelearning/webmcp/commit/14ae813cc4e9fe0d39313f4b1ee5b231746731ad
  10. Web Machine Learning Community Group, Browser and Agent Implementation Status (implementation-status.md, webmachinelearning/webmcp), checked 2026-10-28 (text checked at the raw.githubusercontent.com copy): "Experimental support is added to Leo AI chat." "WebMCP is supported in ChatGPT Desktop." "An Origin Trial is live in Chrome 149." "An Origin Trial is live in Edge 150." — https://github.com/webmachinelearning/webmcp/blob/main/implementation-status.md
  11. MiguelsPizza/WebMCP (GitHub repository description; created 2025-06-13; text checked through the GitHub API): "Bringing the power of MCP to the web" — https://github.com/MiguelsPizza/WebMCP
  12. jasonjmcghee/WebMCP (GitHub repository description; created 2025-03-04; text checked through the GitHub API): "Early WebMCP proposal / implementation - since evolved and worked on by much more capable folks that develop the web" — https://github.com/jasonjmcghee/WebMCP
  13. W3C, WebML WG Teleconference – 14 August 2025 (minutes): "anssik: I also want to acknowledge two individual contributors Alex Nahas and Jason McGhee who both have developed early WebMCP prototypes" — https://www.w3.org/2025/08/14-webmachinelearning-minutes.html
  14. André Cipriani Bandarra, Chrome for Developers, WebMCP is available for early preview, 2026-02-10: "WebMCP is available for prototyping to early preview program participants." — https://developer.chrome.com/blog/webmcp-epp
  15. Alexandra Klepper, François Beaufort, Kasper Kulikowski, Chrome for Developers, WebMCP (AI in Chrome docs), published 2026-05-18, last updated 2026-10-07: "WebMCP is a proposed web standard to help you build and expose structured tools for AI agents." "Chrome Extensions can query and execute WebMCP tools with content scripts." "These extensions are separate from Gemini in Chrome." "Tool discoverability: Clients and browsers must visit a site directly to know if it has callable tools." — https://developer.chrome.com/docs/ai/webmcp
  16. Alexandra Klepper, Chrome for Developers, Join the WebMCP origin trial, 2026-06-09: "In Chrome 149, you can sign up for the WebMCP origin trial." — https://developer.chrome.com/blog/ai-webmcp-origin-trial
  17. Chrome for Developers, 15 updates from Google I/O 2026: Powering the agentic web with new capabilities, tools, and features in Chrome, 2026-05-19: "We’re giving you a first look at WebMCP, a proposed open web standard that lets you expose structured tools like JavaScript functions and HTML forms to browser-based agents." "Gemini in Chrome will soon support WebMCP APIs." — https://developer.chrome.com/blog/chrome-at-io26
  18. blink-dev, Intent to Experiment: WebMCP, 2026-05-15: "Shipping on desktop 157 Origin trial desktop first 149 Origin trial desktop last 156 DevTrial on desktop 146" — https://groups.google.com/a/chromium.org/g/blink-dev/c/gmYffo5WOE8/m/OJxuQRP3AAAJ
  19. Microsoft, Microsoft Edge Origin Trials: WebMCP trial page, checked 2026-10-28: "Origin trial for WebMCP, which allows websites to register tools for use by agents hosted by the site or in Chrome." "Trial Expiration Date March 30, 2027" — https://developer.microsoft.com/en-us/microsoft-edge/origin-trials/trials/0b76fe60-b266-458e-a285-04e375c0c31a
  20. Patrick Brosset, Microsoft Edge Blog, New in Edge for developers – Create better components and make your site agent-ready, 2026-09-21: "We have been actively involved with the Web Machine Learning Community Group, specifying WebMCP: a web API that helps you create efficient, fast, and trusted human-agent collaboration workflows for your site." "To get started, we created a few samples and a browser extension to run and debug your WebMCP tools." — https://blogs.windows.com/msedgedev/2026/09/21/new-in-edge-for-developers-create-better-components-and-make-your-site-agent-ready/
  21. Meta, WebMCP agent tools (Meta Wearables developer docs), updated 2026-10-12: "Your page loads and calls document.modelContext.registerTool() for each tool." "Meta AI picks up your tools and offers them while your app is in front of the user." — https://wearables.developer.meta.com/docs/develop/webapps/agent-tools
  22. Mozilla, WebMCP (standards-positions issue #1412, opened 2026-05-28; label shown; text checked through the GitHub API): "position: neutral" — https://github.com/mozilla/standards-positions/issues/1412
  23. WebKit, WebMCP (standards-positions issue #670, opened 2026-05-28; label shown; text checked through the GitHub API): "position: oppose" — https://github.com/WebKit/standards-positions/issues/670
  24. Brave, [AI Chat]: Add support for the WebMCP protocol to Leo (brave-browser issue #55232, opened 2026-05-05, open; text checked through the GitHub API): "This will allow associated pages to expose tools to AI Chat." — https://github.com/brave/brave-browser/issues/55232
  25. David Eastman, The New Stack, WebMCP turns any Chrome web page into an MCP server for AI agents, 2026-03-17: "But with WebMCP, the action is client-side." — https://thenewstack.io/webmcp-chrome-ai-agents/
  26. Luis Rijo, PPC Land, Chrome 149 origin trial puts WebMCP in developers’ hands at last, 2026-05-20: "MCP servers can run headlessly. WebMCP cannot." — https://ppc.land/chrome-149-origin-trial-puts-webmcp-in-developers-hands-at-last/
  27. Bruno Couriol, InfoQ, WebMCP Standard Proposal for Agentic Web Actuation Now Available in Chrome (Origin Trials), 2026-06-13: "Google recently announced that WebMCP is entering origin trials in Chrome 149." "WebMCP, however, operates entirely on the client side." — https://www.infoq.com/news/2026/06/webmcp-web-agent-standard-chrome/

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