> ## Documentation Index > Fetch the complete documentation index at: https://docs.refactron.dev/llms.txt > Use this file to discover all available pages before exploring further. # Cursor > Add the Refactron MCP server to Cursor with a project .cursor/mcp.json or the global ~/.cursor/mcp.json. Cursor reads MCP servers from a project file or a global one. The project file is the better default: it travels with the repository, so everyone on the team gets the same gate. ## Set it up with your agent One prompt, written for Cursor to read rather than you. It installs the server, registers it, reloads, and proves the tool works with a real verification.
```text theme={null} Set up the Refactron MCP server for yourself in this repository and prove it works before you tell me it is done. Do the steps in order. You are running in Cursor. STEP 1 - Check the prerequisites. Run `node --version`. Refactron needs Node.js 18 or newer. If it is older or missing, stop and tell me. Run `python3 --version`, then check that `pytest` and `coverage` are importable. Coverage attestation is Python-only, and it is what makes a coverage-backed SAFE verdict possible. Without it the server still runs and still gates the change, but every verdict caps at UNPROVEN. STEP 2 - Install the server. Run `which refactron-mcp`, or `where refactron-mcp` on Windows. If it prints a path, go to step 3. Otherwise install it: npm install -g refactron@0.3.0 That puts two binaries on PATH: `refactron` (the CLI) and `refactron-mcp` (the MCP server). If you cannot install globally, install nothing and use the npx form in step 3 instead. Do not use `pip install refactron` for this. The PyPI wrapper provides the `refactron` command only. It does not ship `refactron-mcp`. STEP 3 - Register the server. Create `.cursor/mcp.json` in the repository root, root key "mcpServers". The project file is the better default: it travels with the repository, so the whole team gets the same gate. The global file is ~/.cursor/mcp.json. { "mcpServers": { "refactron": { "command": "refactron-mcp" } } } Merge into the existing "mcpServers" object if the file already has servers. Without a global install, use this instead. The `-p` flag is required, because `refactron-mcp` is a second binary of the `refactron` package and not a package of its own: { "mcpServers": { "refactron": { "command": "npx", "args": ["-y", "-p", "refactron@0.3.0", "refactron-mcp"] } } } STEP 4 - Reload. Cursor reloads MCP servers on a toggle, not on file save. You cannot do this yourself. Tell me to open Cursor Settings, then Tools & Integrations, called MCP in older builds, and switch the `refactron` toggle off and back on. Wait for me before you continue. STEP 5 - Confirm the tool is exposed. Ask me to confirm that `refactron` shows a green indicator in Cursor Settings under Tools & Integrations, with one tool beneath it. Tools are only available in Agent mode. Ask mode does not call tools at all, so if you cannot see the tool, check the mode before you suspect the config. You are looking for a server named `refactron`, version 0.3.0, exposing exactly ONE tool: `verify_change`. If the server is connected but no tool appears, the handshake failed. Prove the binary itself works by sending it one initialize request: echo '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2024-11-05","capabilities":{},"clientInfo":{"name":"probe","version":"1.0"}}}' | refactron-mcp A working server replies on one line with serverInfo.name "refactron". If that works and the client still shows nothing, the fault is the config: check the root key and check that the file parses. STEP 6 - Prove it works with one real verification. Do not skip this. A connected server is not a working server. Pick one small source file that this project's test suite exercises. Propose a real but behaviour-preserving edit to it: reorder the operands of a commutative expression, rename a local variable, that kind of thing. One or two lines. Do NOT write that edit to disk. Call verify_change with the proposal instead: repoRoot the ABSOLUTE path to this repository edits [{ "path": "", "newContent": "" }] testCmd the project's test command, if it is not obvious. For a Python project installed into the environment (an editable `pip install -e .` included), prefix it with PYTHONPATH=. so the tests import the copy being verified rather than the installed one. Use PYTHONPATH=src for a src layout. Verify the change BEFORE it exists on disk. The shadow tree is a copy of the working tree, so if you write the change first and then pass a `git diff` of it, the diff no longer applies and you get "diff did not apply (stale base?)" back instead of a verdict. Verification runs the whole test suite in a shadow copy, so it can take minutes on a real project. That is the work, not a hang. STEP 7 - Report, then stop. Tell me: - which file you wrote, or which command you ran - the exact `verdict` and the exact `reason` from the response - the value of `coverage.tool`: "coverage.py" means coverage was measured, "none" means it was not Apply nothing. The step 6 edit was a probe. Confirm with `git status` that the working tree is exactly as dirty as you found it, and no more. Do not describe a SAFE verdict as "correct", "proven", or "guaranteed". SAFE means the project's own tests ran the changed code and stayed green. It inherits exactly what those tests check, and a weak suite yields a weak SAFE. ```
Prefer to do it yourself? The rest of this page is the same setup by hand. ## Config location | Scope | Path | Applies to | | ------- | ------------------------------------------------------- | ---------------------- | | Project | `.cursor/mcp.json` in the repository root | This project only | | Global | `~/.cursor/mcp.json` (`%USERPROFILE%\.cursor\mcp.json`) | Every project you open | ## Add it Create the file if it does not exist: ```bash theme={null} mkdir -p .cursor ``` ```json theme={null} { "mcpServers": { "refactron": { "command": "refactron-mcp" } } } ``` To pin the version and skip the global install: ```json theme={null} { "mcpServers": { "refactron": { "command": "npx", "args": ["-y", "-p", "refactron@0.3.0", "refactron-mcp"] } } } ``` The `-p` flag is required. `refactron-mcp` is a second binary of the `refactron` package, not a package of its own. ## Verify the connection Open **Cursor Settings** then **Tools & Integrations** (called **MCP** in older builds). `refactron` appears in the list with a green indicator and one tool beneath it: `verify_change`. Then ask the agent in a Chat pane, with Agent mode selected: ```text theme={null} List the tools you have from the refactron MCP server. ``` It should name `verify_change` and nothing else. ## Troubleshooting * **The server shows red or `Client closed`**: Cursor could not launch the command. Run `which refactron-mcp`. If it prints nothing, run `npm install -g refactron@0.3.0`, or switch to the `npx` form above. * **Nothing appears after saving**: Cursor reloads servers on a toggle, not on file save. Switch the `refactron` toggle off and on in the settings pane. * **The tool exists but the agent never calls it**: tools are only available in Agent mode. Ask mode does not call tools. See [Make it verify, not just connect](/mcp/index#make-it-verify-not-just-connect) for a rule that makes the agent verify on its own. * **`repoRoot` errors**: the tool needs an absolute path. Tell the agent to pass the project's absolute path, not `.` and not a path relative to anything. * **A verification takes minutes**: `verify_change` runs your real test suite in a shadow copy. Long is expected on a large suite.