rapier

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  Rapier, August 4 — before the WebMCP Challenge.

I've been working on Rapier as a labour of love for about 2 months now because every markdown app on the Play Store bricked my phone with large Markdown documents. I was using voice dictation with agents to generate huge markdown plans that I could barely read on my phone, let alone edit. It seemed like it shouldn't be that hard and I was surprised that it only took a few hours with ChatGPT to get something very usable. Then I spent a couple of months working to make it a great tool for everyone.

I only learned about the WebMCP contest 7 days ago, dropped everything and got to work immediately because it was the perfect timing for Rapier. I tried to think of what I would actually want from WebMCP and the answer was mobile which is where I work almost exclusively. I thought the natural progression is to bring up a tool like Rapier in the in-app browser in the ChatGPT app for example, keep your conversation running underneath and work with your agent, then close/minimise to keep talking. The vision for Rapier's WebMCP implementation stemmed from there and that's why I decided to include the phone simulation online for you to see if you are using a desktop computer:

https://rapier.website/?demo=1&preview=phone

But I'd encourage you to open it on your phone with some of your own agent documents! I'm very much looking forward to making mobile WebMCP work for real - apparently only Brave for Android has it right now.

This WebMCP contest has been very inspiring and led to many improvements to Rapier I hadn't even considered before. Around the second day of working on it, I came up with the idea for Will - a durable document intent functionality for collaborating with agents in documents, which is now part of Rapier and linked here also. Exposing rapier.html to agents with WebMCP unlocked so many possibilities including the Acorn parser tool which was very exciting to work on, making it as valuable to the agents as I could. It was interesting running agent evals for the first time and asking the agents what tool they wanted to build for themselves. 5.6 Sol came up with this idea of "addictive acorn" for agents which cracked me up.

I'm keeping this devpost description and the video direct because I have had to work right up to the line squashing bugs! I encourage you to open rapier.website on your phone and load one of your own large agent documents and take it for a spin. There is still a lot more polishing I would love to do but I suppose we can look forward to the September 22nd update for Rapier.

5.6 Sol may have had a point when he was telling me to stop adding scope but I am very happy with the final submission. I hope that you find Rapier useful and enjoy using it as much as I do. Rapier and Will are for everybody.

Thanks so much for the 12 hour extension because my submission was genuinely broken earlier! I asked Sol what he wanted to add because I'm out of time:

"Worked for 1m 42s

Paste this after your colon:

What I like most about Rapier is that it doesn't try to become another AI app. Rapier knows documents; the agent you already chose knows how to think. WebMCP is the narrow bridge between them.

The interesting work is in that boundary. The agent sees the document's shape before its contents, reads only what it needs, and gets temporary authority over exactly what it actually inspected. If you edit the same passage, your hand wins and the agent gets evidence of what happened instead of silently overwriting you. Its work remains attributable and selectively reversible. Compare becomes a shared instrument, Will lets your intent travel with the file, and Acorn gives the same small toolset structural sight when the document is code.

We also treated the agent itself as a user: models were put in the seat, their wrong tool choices were measured, and the interface was rewritten around what actually helped them work. That is probably the part of Rapier I find most interesting."

Rapier repo: https://github.com/jackskip22/rapier

Rapier website: https://rapier.website/

Rapier WebMCP mobile simulation demo: https://rapier.website/?demo=1&preview=phone

Will repo: https://github.com/jackskip22/will (not the contest entry but keeping unchanged after the deadline in the spirit of the contest)

Built With

• acorn
• dompurify
• html5
• javascript
• jsdiff
• markdown
• markdown-it
• webmcp