lsp-mcp-server

A lightweight MCP server that exposes type-aware code navigation and fast file search to AI agents via language servers. It manages language server processes on demand, routes LSP requests from MCP tool calls, and returns structured results — letting agents jump to definitions, find references, list symbols, and locate files without reading entire codebases.

Installation

Option 1: Claude Code Plugin (recommended)

One command to clone, install, and register as a Claude Code plugin:

git clone https://github.com/garretpremo/lsp-mcp-server.git ~/.local/share/lsp-mcp-server \
  && cd ~/.local/share/lsp-mcp-server && bun install \
  && bash scripts/install-plugin.sh

Restart Claude Code (or run /reload-plugins) to activate. The plugin adds a skill that guides Claude on when to use each tool, plus the MCP server runs automatically for each project.

Option 2: Per-session (no install)

git clone https://github.com/garretpremo/lsp-mcp-server.git ~/tools/lsp-mcp-server \
  && cd ~/tools/lsp-mcp-server && bun install

Then start Claude Code with:

claude --plugin-dir ~/tools/lsp-mcp-server/plugin

Option 3: Manual MCP config

Add to your project's .mcp.json or ~/.claude/settings.json:

{
  "mcpServers": {
    "lsp-mcp-server": {
      "command": "bun",
      "args": ["run", "/path/to/lsp-mcp-server/src/index.ts", "--project", "."]
    }
  }
}

Option 4: Standalone (any MCP client)

bun run src/index.ts --project /path/to/your/project

Communicates via stdio JSON-RPC — works with any MCP-compatible client.

Related MCP server: Sigil MCP Server

Available Tools

All LSP navigation tools accept optional enrichment flags: includeKind, includeContainer, and includeDocstring.

Configuration

Place a config.json in your project root to override language server commands or the request timeout:

{
  "requestTimeout": 15000,
  "languageServers": {
    "typescript": {
      "command": "typescript-language-server",
      "args": ["--stdio"]
    },
    "java": {
      "command": "jdtls",
      "args": []
    }
  }
}

If no config.json is found, defaults are used. requestTimeout is in milliseconds (default: 10000).

Benchmarks: lsp-mcp-server vs JetBrains MCP

Tested against a 4,381-file Angular/TypeScript project (Nx monorepo).

File Search — "document-viewer"

Document Symbols — reports.service.ts

Go To Definition — HttpClient import

Agent Token Usage (identical tasks, Sonnet model)

Summary

• 6.5x smaller file search responses

• 63x smaller definition lookup responses

• 27% fewer tokens consumed by the agent

• Structured symbol data vs raw text

• True LSP semantics vs text-based grep

Prerequisites

The following language servers must be installed and available on your PATH:

• TypeScript / JavaScript: typescript-language-server

  npm install -g typescript-language-server typescript

• Java: jdtls (Eclipse JDT Language Server)

Language servers are started lazily — only when a file of the matching type is first accessed.

License

MIT