LSP-MCP

Minimal MCP server that bridges any Language Server Protocol (LSP) server to AI agents (e.g. GitHub Copilot CLI). Exposes diagnostics (errors, warnings, info) as lightweight tool calls.

Tools

Tools are generated per server entry, prefixed by the config key:

Tool pattern	Description
{prefix}_get_errors	Compilation errors for a file (or all open files)
{prefix}_get_warnings	Warnings for a file
{prefix}_get_info	Info/hint diagnostics (style rules, analyzers)
lsp_status	All LSP servers' state for debugging

Example with "cs" prefix: cs_get_errors, cs_get_warnings, cs_get_info

Setup

pip install -e .

Configuration

Create .github/lsp.json in your workspace root. Each key is the tool prefix — keep it short:

{
  "lspServers": {
    "cs": {
      "command": "path/to/Microsoft.CodeAnalysis.LanguageServer.exe",
      "args": ["--stdio", "--autoLoadProjects"],
      "fileExtensions": {".cs": "csharp"}
    }
  }
}

Multiple servers generate prefixed tools automatically:

{
  "lspServers": {
    "cs": { "command": "...", "args": [...], "fileExtensions": {".cs": "csharp"} },
    "py": { "command": "pyright-langserver", "args": ["--stdio"], "fileExtensions": {".py": "python"} }
  }
}

This exposes: cs_get_errors, cs_get_warnings, py_get_errors, py_get_warnings, etc.

The fileExtensions map tells the server which languageId to send in textDocument/didOpen. Common extensions (.py, .ts, .go, .rs, etc.) are detected automatically if omitted.

Usage with Copilot CLI

Add to ~/.copilot/mcp-config.json:

{
  "mcpServers": {
    "lsp": {
      "type": "stdio",
      "command": "python",
      "args": ["-m", "lsp_mcp", "--workspace", "/path/to/your/project"]
    }
  }
}

CLI Options

lsp-mcp [--workspace PATH]

• --workspace, -w: Workspace root containing .github/lsp.json (defaults to cwd)

How It Works

1. Reads .github/lsp.json to find the LSP server command
2. Spawns the language server with --stdio and performs the LSP initialize handshake
3. On tool call: opens the file, pulls diagnostics via textDocument/diagnostic, filters by severity
4. Falls back to push diagnostics (publishDiagnostics) if pull returns empty
5. Returns concise JSON with line, column, severity, message, and diagnostic code