Token-efficient code navigation for AI coding agents — SCIP-backed MCP server (MIT)
crux is an MCP server for AI coding agents. It reads a SCIP index of your code. It answers these questions in compact text:
- Where is this symbol? - Who uses this symbol? - Who calls this function? - Which exports are not used?
The agent does not read full files to find these answers. Thus the agent uses fewer tokens.
In paired Codex CLI runs, crux raised correct answers from 66% to 96%. Tokens per correct answer fell by 24%. The Benchmark section has details.
Download the binary for your platform from GitHub Releases:
Platform Binary --- --- macOS (Apple Silicon) crux-aarch64-apple-darwin macOS (Intel) crux-x8664-apple-darwin Linux (x8664) crux-x8664-unknown-linux-gnu Linux (ARM64) crux-aarch64-unknown-linux-gnu Windows (x8664) crux-x8664-pc-windows-msvc.exe
As an alternative, build crux from source:
Run crux self-update to install the latest standalone version. Run crux self-update --check to check for an update without an installation. Halv updates its bundled crux through the app updater.
This command registers the MCP server in ~/.codex/config.toml. It also installs a guidance note in ~/.codex/AGENTS.md.
Use a project note instead of the global note when needed:
This command writes the note to the project's AGENTS.md. The MCP registration remains global.
The prompt-space note is required because Codex CLI ignored MCP server instructions alone: 0 organic adoptions in 60 sessions across three wording variants.
From the project README.
Add the radar badge to your README — it shows your project was picked up by MCP Radar and links to this page:
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