constellation — Claude Code MCP server: code structure without sending source
An MCP server that hands your AI assistant the structure, dependencies and relationships inside a codebase. Raw source files stay where they are.
claude mcp add constellation -e CONSTELLATION_ACCESS_KEY=<CONSTELLATION_ACCESS_KEY> -- npx -y @constellationdev/mcpWhat constellation does
Constellation parses your project locally. A CLI tool walks the code and pulls out structural metadata: functions, classes, variables, imports, calls and references. Only that metadata goes out; the files themselves never leave your machine. The assistant then queries a knowledge graph through the MCP server and gets answers about how the project is put together.
Each git branch keeps its own set of intelligence, so switching branches does not blur the picture. Every request is authenticated, which means CONSTELLATION_ACCESS_KEY is not optional — the server will not start without it.
Setup is one command per platform. On Claude: claude mcp add constellation -e CONSTELLATION_ACCESS_KEY=<CONSTELLATION_ACCESS_KEY> -- npx -y @constellationdev/mcp. You need Node.js v24+ and TypeScript v5.9+ if you plan to build around it. The AGPL-3.0 license matters if you intend to fold the server into a closed-source product.
What it helps with
- find every call site of a given function
- get oriented in an unfamiliar repo before the first edit
- trace dependencies between modules without reading all the code
- check what shifted in the structure after a branch switch
Example prompts for the agent
- Show me which functions call
parseConfigand from where. - Which modules depend on
authon this branch? - Find every class that extends
BaseHandler.
How to install constellation
Platform CLI
claude mcp add constellation -e CONSTELLATION_ACCESS_KEY=<CONSTELLATION_ACCESS_KEY> -- npx -y @constellationdev/mcpReplace <…> with your own values
Platform CLI
codex mcp add constellation --env CONSTELLATION_ACCESS_KEY=<CONSTELLATION_ACCESS_KEY> -- npx -y @constellationdev/mcpReplace <…> with your own values
Config file
{
"mcpServers": {
"constellation": {
"command": "npx",
"args": [
"-y",
"@constellationdev/mcp"
],
"env": {
"CONSTELLATION_ACCESS_KEY": "<CONSTELLATION_ACCESS_KEY>"
}
}
}
}Replace <…> with your own values
Config file
{
"servers": {
"constellation": {
"type": "stdio",
"command": "npx",
"args": [
"-y",
"@constellationdev/mcp"
],
"env": {
"CONSTELLATION_ACCESS_KEY": "<CONSTELLATION_ACCESS_KEY>"
}
}
}
}Replace <…> with your own values
Platform CLI
gemini mcp add -e CONSTELLATION_ACCESS_KEY=<CONSTELLATION_ACCESS_KEY> constellation npx -y @constellationdev/mcpReplace <…> with your own values
Step by step, with commands for each platform: How to add an MCP server to Claude Code, Codex, Cursor, VS Code, Gemini CLI and more
Questions about constellation
How do I install constellation in Claude Code?
Run claude mcp add constellation -e CONSTELLATION_ACCESS_KEY=<CONSTELLATION_ACCESS_KEY> -- npx -y @constellationdev/mcp with your own access key filled in.
What does constellation do?
It parses your project locally and serves the assistant metadata about functions, classes, imports and relationships through a knowledge graph. Source code is not transmitted.
Do I need an access key?
Yes. All requests are authenticated with CONSTELLATION_ACCESS_KEY, and the server will not run without it.
