Playwright and Chrome DevTools MCP servers are the standard for agent-driven web app testing, but their token efficiency is terrible: the screenshot-action-screenshot loop quickly explodes context windows. I've been using browser automation instead of TDD (agents over-mock tests), but needed to solve the token bloat. So I forked the Chrome DevTools MCP server to execute WebMCP tools from client-side JavaScript. It's a drop-in replacement for the Chrome DevTools MCP server but with two added tools (`call_website_tool` & `list_website_tools`). Initial benchmarks show a roughly ~90% decrease in token usage, but other benefits which are harder to measure are speed and determinism (both of which are significantly improved). Benefits: - Free WebMCP support for your website, tools work for in-page or browser agents (in addition to agents using CDP) - Semantic tool definitions improve accessibility - Built on a web standard, no lock-in to my libraries - You can use this as part of your hard-coded E2E tests and make them significantly less flaky and faster All the benchmarks and technical details are in the linked repo or in links at the bottom of the linked repo. On a side note: Much has changed since I wrote the [MCP-B](https://news.ycombinator.com/item?id=44515403) proof of concept a while back. WebMCP is very much on track to be standardized and I've joined the community working group to help form it. My implementation was used to introduce WebMCP at TPAC, I left my job at Amazon to work on it full time, and I found a co-founder to work on it with. I've built a bunch of stuff around WebMCP (much of which I think people can get real utility out of), but have not done a great job of sharing it, so expect to see more WebMCP-related content over the coming days. You can try out WebMCP from meetchar.ai (still very early) but we are looking for alpha testers for an inpage agent. |