MCP Language Server for Claude Code: Setup & Config

What you can do with MCP Language in Claude Code

Choose it to give an MCP coding assistant semantic navigation powered by an existing language server.

• Locate a function definition and its callers through semantic queries.
• Give a coding client language intelligence without embedding an IDE.

Before you start: MCP Language in Claude Code

• Go
• Bridge installed with go install github.com/isaacphi/mcp-language-server@latest
• rust-analyzer installed for this example
• An MCP client and a local workspace

This is the README's Rust example. Replace the workspace path and choose the appropriate installed language server. Other documented configurations cover gopls, pyright, TypeScript, and clangd.

MCP Language Claude Code configuration

1. Choose Claude Code configuration scope

   For MCP Language Server, open Project scope: .mcp.json at the repository root. Project JSON: merge into mcpServers; user scope: use the CLI.

2. Add MCP Language Server to Claude Code

   Use the mcp-language-server entry below in mcpServers. Keep MCP Language Server's documented stdio connection fields and your other Claude Code entries.

3. Check MCP Language Server in Claude Code

   MCP Language Server: Inspect claude mcp list and /mcp status.

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

claude mcp add-json --scope project 'mcp-language-server' '{"type":"stdio","command":"mcp-language-server","args":["--workspace","/Users/you/dev/yourproject/","--lsp","rust-analyzer"],"env":{}}'

MCP Language tools available to Claude Code

MCP Language's stored tool list documents 6 tools; compare it with Claude Code's connected tool list, because the stored list is not a live check.

definition

For MCP Language's definition, review the permission request and arguments in Claude Code before approval.

Resolve a symbol to its source definition.

references

For MCP Language's references, review the permission request and arguments in Claude Code before approval.

Find places in the workspace that use a symbol.

diagnostics

For MCP Language's diagnostics, review the permission request and arguments in Claude Code before approval.

hover

For MCP Language's hover, review the permission request and arguments in Claude Code before approval.

rename_symbol

For MCP Language's rename_symbol, review the permission request and arguments in Claude Code before approval.

Apply a language-aware symbol rename across the project.

edit_file

For MCP Language's edit_file, review the permission request and arguments in Claude Code before approval.

MCP Language: full stored tool descriptions

Troubleshooting MCP Language in Claude Code

• If MCP Language Server fails to start, check mcp-language-server, the working directory, and Claude Code's selected scope; inspect claude mcp list and /mcp.
• MCP Language Server uses stdio here: Claude Code must keep the configured process running; protocol output belongs on stdout and diagnostics on stderr.
• Known limitation: Requires a separately installed language server.
• Known limitation: The underlying server must communicate through stdio.
• Known limitation: The README labels the project beta software.
• General Claude Code troubleshooting lives in the /clients/claude-code guide.

Frequently asked questions