io.github.extensiondev/mcp
extension-dev
Build, run, inspect, and publish browser extensions from any MCP client. 34 tools, 13 browsers.
alive probed 2026-10-15
23tools
16ktokens in Claude Opus 5.5
16ktokens in Claude Code
8.0 %of a 200k context window
9.8ko200k_base estimate
694 msto initialize
14 msto list tools
- Run it
- npx -y @extension.dev/mcp@10.12.0 (stdio, probed in a container with the network off)
- Host
- npmjs.com
- Reports itself as
- extension-dev 10.12.0
- Capabilities
- tools
- Instructions
- 1 644 characters
- Claude count
- Claude Opus 5.5, measured 2026-10-15. Counted again when the tool definitions change. Method.
- Repository
- https://github.com/extensiondev/mcp
- Website
- https://extension.dev
- Registry
- active, updated 2026-10-14 · registry entry
- Reachable
- 1 of the last 1 probe
Most expensive tools
| Tool | Tokens (o200k) | Share of this server |
|---|---|---|
| extension_open | 898 | 9 % |
| extension_dev | 817 | 8 % |
| extension_build | 781 | 8 % |
| extension_dom_snapshot | 728 | 7 % |
| extension_start | 723 | 7 % |
Badge and feed
[](https://mcpcost.ulehla.dev/s/io.github.extensiondev/mcp)
An entry for every probe that changed the result, the tool count or the token cost: Atom feed. Add it to a feed reader or a Slack RSS app to hear when the server stops answering or its tool set grows.