mcp-language-server MCP — Use Cases, Install & Live Demo

Why use it

Key features

LSP semantic operations: definition, references, rename, hover, diagnostics
Works with any stdio LSP (gopls, rust-analyzer, pyright, tsserver, clangd)
Single Go binary, easy install
edit_file uses LSP-backed rename for correctness
One MCP instance per LSP; compose multiple for polyglot repos

Live Demo

What it looks like in practice

language-server.replay ▶ ready

0/0

Install

Pick your client

~/Library/Application Support/Claude/claude_desktop_config.json · Windows: %APPDATA%\Claude\claude_desktop_config.json

{
  "mcpServers": {
    "language-server": {
      "command": "TODO",
      "args": [
        "See README: https://github.com/isaacphi/mcp-language-server"
      ],
      "_inferred": true
    }
  }
}

Open Claude Desktop → Settings → Developer → Edit Config. Restart after saving.

~/.cursor/mcp.json · .cursor/mcp.json

{
  "mcpServers": {
    "language-server": {
      "command": "TODO",
      "args": [
        "See README: https://github.com/isaacphi/mcp-language-server"
      ],
      "_inferred": true
    }
  }
}

Cursor uses the same mcpServers schema as Claude Desktop. Project config wins over global.

VS Code → Cline → MCP Servers → Edit

{
  "mcpServers": {
    "language-server": {
      "command": "TODO",
      "args": [
        "See README: https://github.com/isaacphi/mcp-language-server"
      ],
      "_inferred": true
    }
  }
}

Click the MCP Servers icon in the Cline sidebar, then "Edit Configuration".

~/.codeium/windsurf/mcp_config.json

{
  "mcpServers": {
    "language-server": {
      "command": "TODO",
      "args": [
        "See README: https://github.com/isaacphi/mcp-language-server"
      ],
      "_inferred": true
    }
  }
}

Same shape as Claude Desktop. Restart Windsurf to pick up changes.

~/.continue/config.json

{
  "mcpServers": [
    {
      "name": "language-server",
      "command": "TODO",
      "args": [
        "See README: https://github.com/isaacphi/mcp-language-server"
      ]
    }
  ]
}

Continue uses an array of server objects rather than a map.

~/.config/zed/settings.json

{
  "context_servers": {
    "language-server": {
      "command": {
        "path": "TODO",
        "args": [
          "See README: https://github.com/isaacphi/mcp-language-server"
        ]
      }
    }
  }
}

Add to context_servers. Zed hot-reloads on save.

claude mcp add language-server -- TODO 'See README: https://github.com/isaacphi/mcp-language-server'

One-liner. Verify with claude mcp list. Remove with claude mcp remove.

Use Cases

Real-world ways to use mcp-language-server

How to rename a symbol safely across a repo

👤 Polyglot devs using agents ⏱ ~15 min intermediate

When to use: You want a rename that understands scope, not a find-replace.

Prerequisites

Go installed — brew install go
The LSP for your language — gopls: go install golang.org/x/tools/gopls@latest; pyright: pip install pyright; etc.
Install the MCP — go install github.com/isaacphi/mcp-language-server@latest

Flow

Start the MCP pointed at your workspace + LSP

Add MCP config: command=mcp-language-server, args=['--workspace','.','--lsp','gopls'].✓ Copied

→ Tools appear
Find references first

references for symbol 'LegacyAuth' in file auth.go.✓ Copied

→ Precise cross-repo references
Rename

rename_symbol 'LegacyAuth' -> 'Auth' at the definition site.✓ Copied

→ All callsites updated correctly

Outcome: Semantically-correct rename across the repo.

Pitfalls

Agent falls back to text find-replace when the tool fails — Verify diagnostics after rename — compile errors mean the LSP refused and the agent cheated

Combine with: github

How to let the agent navigate like you do in an IDE

👤 Agent users tired of re-grepping ⏱ ~10 min beginner

When to use: Agent keeps reading whole files to find one function.

Flow

Query definition

definition for 'computeTax' in src/billing.ts.✓ Copied

→ Exact file:line location
Pull diagnostics

diagnostics for the current file.✓ Copied

→ Red squigglies from the LSP

Outcome: Agent navigates like an IDE user.

Pitfalls

LSP not initialized — slow first call — Warm up with a list of files in the workspace; pyright especially is slow to index

Combine with: contextplus

How to run multiple LSPs for a polyglot monorepo

👤 Devs on Go+TS+Python monorepos ⏱ ~25 min advanced

When to use: You want semantic ops in every language.

Flow

Register one MCP per LSP

Add 3 MCP entries: lsp-go (gopls), lsp-ts (tsserver), lsp-py (pyright), each scoped to its workspace subfolder.✓ Copied

→ 3 sets of language-specific tools
Use them in turn

For TypeScript questions use lsp-ts:definition; for Go use lsp-go:definition.✓ Copied

→ Correct semantics per language

Outcome: Semantically-aware navigation across all languages.

Pitfalls

Agent forgets which MCP handles which language — Rename tool prefixes descriptively and mention in your project memory

Combinations

Pair with other MCPs for X10 leverage

language-server + contextplus

Combine LSP navigation with semantic/embedding search for broader queries

Use language-server's references for exact usages of computeTax, then contextplus semantic search to find conceptually-related functions.✓ Copied

language-server + github

Rename + commit + PR

Rename LegacyAuth to Auth via the LSP, commit to a new branch, open a PR.✓ Copied

Tools

What this MCP exposes

Tool	Inputs	When to call	Cost
definition	file: str, symbol_or_position	Jump to declaration	free (local LSP)
references	file: str, symbol_or_position	Find usages	free
diagnostics	file: str	Check errors/warnings	free
hover	file, position	Type info / docs for a symbol	free
rename_symbol	file, position, new_name	Safe rename	free
edit_file	file, edits	LSP-validated edit	free

Cost & Limits

What this costs to run

API quota: None — local LSP
Tokens per call: Small — LSP responses are compact
Monetary: Free
Tip: Use LSP-backed tools before embedding search — often cheaper and more precise.

Security

Permissions, secrets, blast radius

Minimum scopes: Filesystem read/write to the workspace

Credential storage: None

Data egress: Localhost only; LSP runs in-process

Never grant: Don't point it at workspaces with secrets — LSPs sometimes index them

edit_file respects LSP validation but doesn't guarantee atomicity across multi-file edits.

Troubleshooting

Common errors and fixes

tool returns 'LSP not ready'

First call triggers initialization — retry after 2-5 seconds, or warm up with a hover call.

gopls: 'no packages found'

Point workspace at the module root (where go.mod is), not a subfolder.

Verify: go env GOMOD

pyright slow on big repos

Configure pyrightconfig.json to exclude vendored dirs.

rename_symbol reports success but compile still fails

Rename touched a string literal or reflection-based code the LSP can't see. Check grep for the old name.

Alternatives

mcp-language-server vs others

Alternative	When to use it instead	Tradeoff
Context+	You want embedding + memory graph rather than LSP semantics	Not as precise on rename/references
Serena MCP	You want LSP with higher-level refactors	Different setup; Python-based

More

Resources

📖 Read the official README on GitHub

🐙 Browse open issues

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