Claude Desktop uses an MCP config file to know which servers to call. Adding CoreThesis is a single edit in that file.
Open ~/Library/Application Support/Claude/claude_desktop_config.json (create it if missing).
Inside the mcpServers object, paste the CoreThesis block from /docs. Substitute <YOUR_API_KEY> with a key from /keys.
Quit Claude Desktop entirely (Cmd-Q) and relaunch it. The MCP is loaded on boot; a reload won't pick it up.
Confirm it worked by typing "start here" — Claude will call CoreThesis and come back with a short tour plus prompts you can copy. That call is free.
Or go straight at it: "Pull the latest 10-Q for NVDA and flag any new risk factors."
If Claude says it doesn't have the tool, double-check the JSON is valid (strict quoting, no trailing commas) and that the config path is right.