WebMCP Proposal

For accessibility, that's a client consideration typically, the agent using the MCP server would be responsible for making its output accessible. I don't think the intention is to let webapps define how their output is displayed to end users, but to define outputs for agents instead.

For security, other than what the MCP protocol itself provides, what should be defined?

I think it's a draft, there is still discussion about it, they might not have reached a point where there consensus for those categories. But I'm curious to hear your thoughts.

1. This is a contextual API built into each page. Historically site's can offer an API, but that API a parallel experience, a separate machine-to-machine channel, that doesn't augment or extend the actual user session. The MCP API offered here is one offered by the page (not the server/site), in a fully dynamic manner (what's offered can reflect what the state of the page is), that layers atop user session. That's totally different.

2. This opens an expectation that sites have a standard means of control available. This has two subparts:

2a. There's dozens of different API systems available, to pick from, to expose your site. Github got half way from rest to graphql then turned back. Some sites use ttrpc or capnweb or gproto. There hasn't actually been one accepted way for machines to talk to your site, there's been a fractal maze of offerings on the web. This is one consistent offering mirroring what everyone is already using now anyways.

2b. Offering APIs for your site has gone out of favor in general. It often has had high walls and barriers when it is available. But now the people putting their fingers in that leaky damn are patently clearly Not Going To Make It, the LLM's will script & control the browser if they have to, and it's much much less pain to just lean in to what users want to do, and to expose a good WebMCP API that your users can enjoy to be effective & get shit done, like they have wanted to do all along. If webmcp takes off at all, it will reset expectations, that the internet is for end users, and that their agency & their ability to work your site as they please via their preferred modalities is king. WebMCP directs us towards a rfc8890 complaint future, by directly enabling site agency. https://datatracker.ietf.org/doc/html/rfc8890

I'm not sure if this is really all that much better than, say, a swagger API. The js interface has the double edge of access to your cookies and such.

I tried to play along at home some, play with rust accesskit crate. But man I just could not get Orcas or other basic tools to run, could not get a starting point. Highly discouraging. I thought for sure my browser would expose accessibility trees I could just look at & tweak! But I don't even know if that's true or not yet! Very sad personal experience with this.

> Integrating agents into it prevents fragmentation of their service and allows them to keep ownership of their interface, branding and connection with their users

Looking at the contrived examples given, I just don't see how they're achieving this. In fact it looks like creating MCP specific tools will achieve exactly the opposite. There will immediately be two ways to accomplish a thing and this will result in a drift over time as developers need to take into account two ways of interacting with a component on screen. There should be no difference, but there will be.

Having the LLM interpret and understand a page context would be much more in line with assistive technologies. It would require site owners to provide a more useful interface for people in need of assistance.

That, or they expect that MCP clients should also be running a headless Chrome to detect JS-only MCP endpoints.

I do like agent skills, but I’m really not convinced by the hype that they make MCP redundant.

Think of it like an "IDE actions". Done right, there's no need to ever use the GUI.

As opposed to just being documentation for how to use the IDE with desktop automation software.

Every generation needs its own acronyms and specifications. If a new one looks like an old one likely the old one was ahead of its time.

It's great they are working on standardizing this so websites don't have to integrate with LLMs. The real opportunity seems to be able to automatically generate the tool calls / MCP schema by inspecting the website offline - I automated this using PLayright MCP.

This is what permissions are for.

Instead of parsing or screen-shooting the current page to understand the context, an AI agent running in the browser can query the page tools to extract data or execute actions without dealing with API authentication.

It's a pragmatic solution. An AI agent, in theory, can use the accessibility DOM to improve access to the page (or some HTML data annotation); however, it doesn't provide it with straightforward information about the actions it can take on the current page.

I see two major roadblocks with this idea:

1. Security: Who has access to these MCPs? This makes it easier for browser plugins to act on your behalf, but end users often don't understand the scope of granting plugins access to their pages.

2. Incentive: Exposing these tools makes accessing website data extremely easy for AI agents. While that's great for end users, many businesses will be reluctant to spend time implementing it (that's the same reason social networks and media websites killed RSS... more flexibility for end users, but not aligned with their business incentives)

But I’d happily add a little mcp server to it in js, if that means someone else can point their LLM at it and be taught how to play sudoku.

Instead of letting the agent call a server (MCP), the agent downloads javascript and executes it itself (WebMCP).

I wanted to make FOSS codegen that was not locked behind paywalls + had wasm plugins to extend it.