MCP Language Server

This is an MCP server that runs and exposes a language server to LLMs. Not a language server for MCP, whatever that would be.

Demo

mcp-language-server helps MCP enabled clients navigate codebases more easily by giving them access semantic tools like get definition, references, rename, and diagnostics.

Setup

1. Install Go: Follow instructions at https://golang.org/doc/install
2. Install or update this server: go install github.com/isaacphi/mcp-language-server@latest
3. Install a language server: follow one of the guides below
4. Configure your MCP client: follow one of the guides below

Go (gopls)

<strong>Install gopls</strong>: <code>go install golang.org/x/tools/gopls@latest</code>
<strong>Configure your MCP client</strong>: This will be different but similar for each client. For Claude Desktop, add the following to <code>~/Library/Application\ Support/Claude/claude_desktop_config.json</code>

{ "mcpServers": { "language-server": { "command": "mcp-language-server", "args": ["--workspace", "/Users/you/dev/yourproject/", "--lsp", "gopls"], "env": { "PATH": "/opt/homebrew/bin:/Users/you/go/bin", "GOPATH": "/users/you/go", "GOCACHE": "/users/you/Library/Caches/go-build", "GOMODCACHE": "/Users/you/go/pkg/mod" } } } }

Note: Not all clients will need these environment variables. For Claude Desktop you will need to update the environment variables above based on your machine and username:

Rust (rust-analyzer)

<strong>Install rust-analyzer</strong>: <code>rustup component add rust-analyzer</code>
<strong>Configure your MCP client</strong>: This will be different but similar for each client. For Claude Desktop, add the following to <code>~/Library/Application\ Support/Claude/claude_desktop_config.json</code>

{ "mcpServers": { "language-server": { "command": "mcp-language-server", "args": [ "--workspace", "/Users/you/dev/yourproject/", "--lsp", "rust-analyzer" ] } } }

Python (pyright)

<strong>Install pyright</strong>: <code>npm install -g pyright</code>
<strong>Configure your MCP client</strong>: This will be different but similar for each client. For Claude Desktop, add the following to <code>~/Library/Application\ Support/Claude/claude_desktop_config.json</code>

{ "mcpServers": { "language-server": { "command": "mcp-language-server", "args": [ "--workspace", "/Users/you/dev/yourproject/", "--lsp", "pyright-langserver", "--", "--stdio" ] } } }

Typescript (typescript-language-server)

<strong>Install typescript-language-server</strong>: <code>npm install -g typescript typescript-language-server</code>
<strong>Configure your MCP client</strong>: This will be different but similar for each client. For Claude Desktop, add the following to <code>~/Library/Application\ Support/Claude/claude_desktop_config.json</code>

{ "mcpServers": { "language-server": { "command": "mcp-language-server", "args": [ "--workspace", "/Users/you/dev/yourproject/", "--lsp", "typescript-language-server", "--", "--stdio" ] } } }

C/C++ (clangd)

<strong>Install clangd</strong>: Download prebuilt binaries from the official LLVM releases page or install via your system's package manager (e.g., <code>apt install clangd</code>, <code>brew install clangd</code>).
<strong>Configure your MCP client</strong>: This will be different but similar for each client. For Claude Desktop, add the following to <code>~/Library/Application\\ Support/Claude/claude_desktop_config.json</code>

{ "mcpServers": { "language-server": { "command": "mcp-language-server", "args": [ "--workspace", "/Users/you/dev/yourproject/", "--lsp", "/path/to/your/clangd_binary", "--", "--compile-commands-dir=/path/to/yourproject/build_or_compile_commands_dir" ] } } } Note: Replace /path/to/your/clangd_binary with the actual path to your clangd executable. --compile-commands-dir should point to the directory containing your compile_commands.json file (e.g., ./build, ./cmake-build-debug). Ensure compile_commands.json is generated for your project for clangd to work effectively.

Other

I have only tested this repo with the servers above but it should be compatible with many more. Note:
<ul>
  <li>The language server must communicate over stdio.</li>
  <li>Any aruments after <code>--</code> are sent as arguments to the language server.</li>
  <li>Any env variables are passed on to the language server.</li>
</ul>

Tools

• definition: Retrieves the complete source code definition of any symbol (function, type, constant, etc.) from your codebase.
• references: Locates all usages and references of a symbol throughout the codebase.
• diagnostics: Provides diagnostic information for a specific file, including warnings and errors.
• hover: Display documentation, type hints, or other hover information for a given location.
• rename_symbol: Rename a symbol across a project.
• edit_file: Allows making multiple text e