mclsp

mclsp is an MCP server that bridges coding agents to Language Server Protocol (LSP) capabilities. You can configure one or more LSP servers (for example, TypeScript, Rust, Ruby) and mclsp exposes their features as MCP tools such as go-to-definition, find references, diagnostics, and rename. Servers start lazily on first use, so there’s no startup cost for languages you don’t touch. To begin, install the MCP framework, then add the lsp server via the Quick Start, which wires mclsp into your project and prepares a mclsp.yaml configuration. Once configured, you can invoke standard LSP tools (e.g., goto_definition, hover, document_symbols) through the MCP interface. Some servers include extra extensions (like TypeScript-specific go-to-source-definition and organize-imports) that extend the available tools.

Prerequisites:

• Node.js and npm installed on your system
• Access to run npx (comes with npm)

1. Install the MCP framework (if you haven’t already) and add the LSP bridge:

   claude mcp add lsp -- npx -y mclsp

2. Create the configuration file in your project root named mclsp.yaml and configure your LSP servers. Example for TypeScript:

   servers: typescript: command: ["typescript-language-server", "--stdio"] filePatterns: ["/*.ts", "/.tsx", "**/.js", "**/*.jsx"]

   You can add more servers (e.g., Rust, Ruby) with their respective command arrays and filePatterns as shown in the README.

3. Run the MCP command to start listening for tool invocations (the server will start lazily when a tool is used):

   claude mcp run

4. Verify integration by invoking a tool (e.g., goto_definition) against a file that matches one of the configured filePatterns.

Tips:

• Each server entry supports command (string array), filePatterns, optional initializationOptions, rootUri, and env for environment variables.
• Tools are invoked with position-based parameters: file (relative path), line (1-indexed), and col (1-indexed).
• Servers start lazily on first use to minimize startup costs.
• If you add custom server extensions or additional language support, place them under src/extensions/ as described in the contributing section.
• Common issues often relate to incorrect filePatterns, missing initializationOptions, or environment variable misconfigurations for the LSP server process.