jasonjmcghee
koolala
How much of this can or can't be done by a Extension or Bookmarklet running JS in a page? What is your biggest dream from standardizing this?
jasonjmcghee
If there's a standard instead of needing to download the Jira mcp server, you just visit their website and all the tools are described and usable from there.
Or put differently, as a company / group / individual, instead of needing to build and distribute an mcp server and public API, you can just support WebMCP.
Another alternative is LLMs / agents operating playwright or the equivalent which will likely be less reliable and consume more tokens. (By a fair margin)
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nsonha
it seems like a cleaner approach to declare a handful of tools that users can approve/ask for granularily, than just say "my website can run any wacky script, here is some bookmarklet, nerds" or the very generic permission model of browser extensions
koolala
Couldn't that be solved with a simple bookmarklet permission model? The script would request the same pop-up features as a website?
huflungdung
[dead]
miguelspizza
Hey glad to see Jason getting the credit he deserves! He was grokking WebMCP long before anyone else.
If anyone wants to test out WebMCP, you can go to: https://webmcp.sh/ (this is a WebMCP server)
With the MCP-B chrome extension (this is a WebMCP client): https://chromewebstore.google.com/detail/mcp-b-extension/dao...
and use it to call WebMCP tools
mrasong
Tried Claude’s Chrome control feature before, it totally blew my mind.
Didn’t expect WebMCP to let you build custom MCP clients too. That’s actually way more flexible!
dogma1138
Sitemap.xml is back.
pjmlp
Never went away, we always have to deliver it somehow on our projects.
tobyjsullivan
I had to skim through this a couple times before I realized that I still need to run an MCP server locally. This is basically a proxy between an LLM and the proposed protocol.
It’s a nice proof of concept.
And makes sense that the goal would be for LLM clients to adopt and support the standard natively. Then the proxy won’t be necessary.
koolala
ChatGPT couldn't websocket connect to it directly in your browser?
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westurner
W3C specs are written with respec: ReSpec docs: https://respec.org/docs/#w3c-documents
W3C Process document > 3.4. Chartered Groups: Working Groups and Interest Groups: https://www.w3.org/policies/process/#GAGeneral
There's WebGPU, WebNN, window.ai, Prompt API, Summarizer API, Writer API, Rewriter API, Language Detector API, Translator API ; and now WebMCP
WebNN: https://www.w3.org/TR/webnn/
webmachinelearning/prompt-api > "Explainer for the Prompt API": https://github.com/webmachinelearning/prompt-api
https://developer.chrome.com/docs/ai/built-in :
> Standardization effort: We're working to standardize all of these APIs for cross-browser compatibility.
> The Language Detector API and Translator API have been adopted by the W3C WebML Working Group. We've asked Mozilla and WebKit for their standards positions.
> The Summarizer API, Writer API, and Rewriter API have also been adopted by the W3C WebML Working Group. We've asked asked Mozilla and WebKit for their standards positions.
webmachinelearning/webmcp: https://github.com/webmachinelearning/webmcp
jasonjmcghee/WebMCP: https://github.com/jasonjmcghee/WebMCP
Having worked on at least one web app with a name that started with "Web", I'm not surprised.
/? mcp chrome: https://hn.algolia.com/?dateRange=all&page=0&prefix=false&qu... :
- "Show HN: We packaged an MCP server inside Chromium" (today) https://news.ycombinator.com/item?id=45618536 re: browseros-mcp: https://github.com/browseros-ai/BrowserOS/blob/main/docs/bro...
- "Chrome DevTools (MCP) for your AI agent" https://developer.chrome.com/blog/chrome-devtools-mcp .. https://news.ycombinator.com/item?id=45412734 (September 2025) .. :
> We're launching today a public preview for the new Chrome DevTools Model Context Protocol (MCP) server, bringing the power of Chrome DevTools to AI coding assistants.
> Coding agents face a fundamental problem: they are not able to see what the code they generate actually does when it runs in the browser. They're effectively programming with a blindfold on.
> The Chrome DevTools MCP server changes this. AI coding assistants are able to debug web pages directly in Chrome, and benefit from DevTools debugging capabilities and performance insights. This improves their accuracy when identifying and fixing issues.
How could the Chrome DevTools MCP be integrated with the Gemini Computer Use model?
From https://news.ycombinator.com/item?id=45543923 :
> Competency Story: The customer and product owner can write BDD tests in order to validate the app against the requirements
> Prompt: Write playwright tests for #token_reference, that run a named factored-out login sequence, and then test as human user would that: when you click on Home that it navigates to / (given browser MCP and recently the Gemini 2.5 Computer Operator model)
"Introducing the Gemini 2.5 Computer Use model" (October 2025) https://blog.google/technology/google-deepmind/gemini-comput...
Could this help with accessibility reviews?
"Lighthouse accessibility score" https://developer.chrome.com/docs/lighthouse/accessibility/s...
awesome-a11y > Tools: https://github.com/brunopulis/awesome-a11y/blob/main/topics/...
ocdtrekkie
This explains all the new random GPO settings I had to go disable at the office this week! (A lot of users are reporting performance issues with browsers, seems like all the browsers are adding AI things... seems like a good place to start.)
sublinear
From https://modelcontextprotocol.io/docs/getting-started/intro
> What can MCP enable? 1) Agents can access your Google Calendar and Notion, acting as a more personalized AI assistant. 2) Claude Code can generate an entire web app using a Figma design. 3) Enterprise chatbots can connect to multiple databases across an organization, empowering users to analyze data using chat. 4) AI models can create 3D designs on Blender and print them out using a 3D printer.
Sure 1 and 3 make sense if they mean "summarize" and not "analyze", 4 maybe, but 2... Oh I don't know where to begin other than to say that even really smart humans have a very hard time dealing with that task based on a figma doc. Wouldn't it make more sense to generate the figma doc if they're already that awful to begin with?
meindnoch
[flagged]
Surprised to see this on HN front-page.
A lot has happened since I proposed / built this.
WebMCP is being incubated in W3C / webmachinelearning, so highly recommend checking that out as it's what will turn into WebMCP being in your browser.
https://github.com/webmachinelearning/webmcp