open-devtools

All-in-one MCP server providing LSP diagnostics, linting, and code formatting for AI coding assistants.

What is this?

open-devtools is a comprehensive Model Context Protocol (MCP) server that brings professional developer tooling to AI assistants like Claude Desktop, Cline, and other MCP-compatible applications. It combines:

LSP Diagnostics - Real-time errors, warnings, and hints from language servers
Linting - Code quality checks via ESLint, Biome, and other linters
Formatting - Auto-format code with industry-standard tools

Features

🔍 9 LSP Servers - ESLint, Biome, TypeScript, Python, Go, Ruby, Rust, C#, Java
🎨 11 Formatters - Prettier, Biome, gofmt, ruff, rubocop, clang-format, and more
⚡ 40+ File Extensions - Support for all major programming languages
🚀 Zero Configuration - Works out of the box with auto-detection
⚙️ Fully Configurable - Customize servers, formatters, and file extensions
🔧 3 MCP Tools - get_diagnostics, format_file, lint_file

Supported Languages

LSP Servers (Diagnostics & Linting)

Language	Server	Extensions	Features
JavaScript/TypeScript	ESLint	`.js`, `.jsx`, `.ts`, `.tsx`, `.vue`, `.mjs`, `.cjs`	Linting, code quality
JavaScript/TypeScript/JSON	Biome	`.js`, `.jsx`, `.ts`, `.tsx`, `.json`, `.jsonc`	Fast linting & formatting
TypeScript/JavaScript	TypeScript	`.ts`, `.tsx`, `.js`, `.jsx`, `.mjs`, `.cjs`, `.mts`, `.cts`	Type checking, intellisense
Python	Pyright	`.py`, `.pyi`	Type checking, imports
Go	gopls	`.go`	Go tooling
Ruby	ruby-lsp	`.rb`, `.rake`	Ruby analysis
Rust	rust-analyzer	`.rs`	Rust diagnostics
C#	OmniSharp	`.cs`	C# analysis
Java	JDTLS	`.java`	Java diagnostics

Formatters

Formatter	Languages	Extensions
Prettier	JS/TS, HTML, CSS, Markdown, JSON, YAML	20+ extensions
Biome	JS/TS, JSON	Same as Prettier
gofmt	Go	`.go`
ruff	Python	`.py`, `.pyi`
rubocop	Ruby	`.rb`, `.rake`, `.gemspec`, `.ru`
standardrb	Ruby	`.rb`, `.rake`, `.gemspec`, `.ru`
clang-format	C/C++	`.c`, `.cpp`, `.h`, etc.
ktlint	Kotlin	`.kt`, `.kts`
zig fmt	Zig	`.zig`, `.zon`
mix format	Elixir	`.ex`, `.exs`, etc.
htmlbeautifier	ERB/HTML	`.erb`, `.html.erb`

Installation

Prerequisites

Important: The MCP server does not auto-install dependencies. You must manually install the language servers and formatters you need.

Auto-installed (via bunx): The following tools download automatically on first use:

ESLint language server (requires ESLint installed in your project)
TypeScript language server
Biome language server and formatter (formatter requires biome.json config)
Prettier formatter (requires Prettier in your project's package.json)

Install other tools you'll use:

# JavaScript/TypeScript - install in your project for ESLint/Prettier to work
npm install --save-dev eslint prettier

# Python  
pip install pyright ruff

# Go
go install golang.org/x/tools/gopls@latest

# Ruby
gem install ruby-lsp rubocop standardrb

# Rust
rustup component add rust-analyzer

# C/C++, Kotlin, Zig, Elixir (install as needed)
# See language-specific documentation

Using with Claude Desktop

Add to your Claude Desktop configuration:

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

{
  "mcpServers": {
    "open-devtools": {
      "command": "npx",
      "args": ["-y", "open-devtools"]
    }
  }
}

Using with Cline (VS Code)

{
  "mcpServers": {
    "open-devtools": {
      "command": "npx",
      "args": ["-y", "open-devtools"]
    }
  }
}

Using with Amp

{
  "amp.mcpServers": {
    "open-devtools": {
      "command": "npx",
      "args": ["-y", "open-devtools"]
    }
  }
}

Available Tools

`get_diagnostics`

Get LSP diagnostics (errors, warnings, hints) for a file. Automatically starts the appropriate language server if needed.

Parameters:

filePath (string, required) - Absolute path to the file

Example:

Diagnostics for /path/to/file.ts:

ERROR [10:5] Cannot find name 'foo'
WARN [15:12] 'bar' is declared but never used
INFO [20:1] File is a CommonJS module

`format_file`

Format a file using the appropriate formatter. Automatically detects the formatter based on file extension and project configuration.

Parameters:

filePath (string, required) - Absolute path to the file

Example:

Successfully formatted /path/to/file.ts using prettier

`lint_file`

Get linting information for a file.

Note: Most linting is handled by LSP servers through get_diagnostics (ESLint, Biome, etc.). Use get_diagnostics for comprehensive linting diagnostics.

Configuration

Configure LSP servers and formatters using environment variables:

{
  "mcpServers": {
    "open-devtools": {
      "command": "npx",
      "args": ["-y", "open-devtools"],
      "env": {
        "OPEN_DEVTOOLS_LSP_CONFIG": "{\"eslint\":{\"disabled\":false}}",
        "OPEN_DEVTOOLS_FORMATTER_CONFIG": "{\"prettier\":{\"disabled\":false}}"
      }
    }
  }
}

LSP Configuration Structure

{
  "server-name": {
    "disabled": false,           // Set to true to disable
    "command": ["cmd", "args"],  // Override command
    "extensions": [".ext"],      // Override file extensions
    "env": {                     // Environment variables
      "VAR": "value"
    },
    "initialization": {}         // LSP initialization options
  }
}

Formatter Configuration Structure

{
  "formatter-name": {
    "disabled": false,              // Set to true to disable
    "command": ["cmd", "$FILE"],    // Override command ($FILE placeholder)
    "extensions": [".ext"],         // Override file extensions
    "environment": {                // Environment variables
      "VAR": "value"
    }
  }
}

Available Server and Formatter Names

LSP Servers:

eslint - JavaScript/TypeScript linting
biome - Fast JS/TS/JSON linting & formatting
typescript - TypeScript type checking
pyright - Python type checking
gopls - Go language server
ruby-lsp - Ruby language server
rust-analyzer - Rust language server
omnisharp - C# language server
jdtls - Java language server

Formatters:

prettier - Multi-language formatter
biome - Fast JS/TS/JSON formatter
gofmt - Go formatter
ruff - Python formatter
rubocop - Ruby formatter with auto-correct
standardrb - Ruby standard style formatter
clang-format - C/C++ formatter
ktlint - Kotlin formatter
zig - Zig formatter
mix - Elixir formatter
htmlbeautifier - ERB/HTML formatter

Configuration Examples

Disable Built-in Servers/Formatters

{
  "mcpServers": {
    "open-devtools": {
      "command": "npx",
      "args": ["-y", "open-devtools"],
      "env": {
        "OPEN_DEVTOOLS_LSP_CONFIG": "{\"typescript\":{\"disabled\":true}}",
        "OPEN_DEVTOOLS_FORMATTER_CONFIG": "{\"prettier\":{\"disabled\":true}}"
      }
    }
  }
}

Override File Extensions

{
  "env": {
    "OPEN_DEVTOOLS_LSP_CONFIG": "{\"biome\":{\"extensions\":[\".ts\",\".tsx\",\".js\"]}}",
    "OPEN_DEVTOOLS_FORMATTER_CONFIG": "{\"prettier\":{\"extensions\":[\".js\",\".ts\"]}}"
  }
}

Add Custom LSP Server

{
  "env": {
    "OPEN_DEVTOOLS_LSP_CONFIG": "{\"lua-lsp\":{\"command\":[\"lua-language-server\",\"--stdio\"],\"extensions\":[\".lua\"]}}"
  }
}

Add Custom Formatter

{
  "env": {
    "OPEN_DEVTOOLS_FORMATTER_CONFIG": "{\"stylua\":{\"command\":[\"stylua\",\"$FILE\"],\"extensions\":[\".lua\"]}}"
  }
}

Configure with Environment Variables

{
  "env": {
    "OPEN_DEVTOOLS_LSP_CONFIG": "{\"eslint\":{\"env\":{\"NODE_ENV\":\"development\"}}}"
  }
}

Multiple Configurations

{
  "env": {
    "OPEN_DEVTOOLS_LSP_CONFIG": "{\"typescript\":{\"disabled\":true},\"pyright\":{\"disabled\":true},\"eslint\":{\"env\":{\"DEBUG\":\"true\"}}}"
  }
}

How It Works

Auto-Detection: Detects language servers and formatters based on file extension and project configuration
Smart Caching: Reuses language server instances across multiple requests to the same project
Project-Aware: Finds project roots (e.g., package.json, tsconfig.json, go.mod) automatically
Config-Driven: Respects your project's formatter configs (.prettierrc, biome.json, etc.)

Troubleshooting

No diagnostics/linting

Ensure the language server is installed (which typescript-language-server, etc.)
Check that your file is part of a valid project
Some servers require config files (e.g., tsconfig.json for TypeScript)

Formatter not found

Install the formatter for your language. See Installation.

ESLint not working

Install ESLint language server: npm install -g vscode-eslint-language-server
Ensure ESLint is configured in your project (.eslintrc.* or eslint.config.js)
Make sure ESLint is installed in your project: npm install --save-dev eslint

Contributing

Contributions are welcome! Please follow these steps:

Fork the repository: https://github.com/thenamankumar/open-devtools
Create a feature branch: git checkout -b feature/your-feature
Make your changes and add tests
Run tests: bun test
Run typecheck: bun run typecheck
Commit your changes: git commit -am 'Add some feature'
Push to the branch: git push origin feature/your-feature
Submit a pull request

Development Setup

# Clone the repository
git clone https://github.com/thenamankumar/open-devtools.git
cd open-devtools

# Install dependencies
bun install

# Run tests
bun test

# Run typecheck
bun run typecheck

# Run in development mode
bun run dev

Adding New LSP Servers or Formatters

Use the configuration system to test custom servers/formatters before submitting a PR. See the Configuration section for examples.

Issues & Support

Bug Reports: GitHub Issues
Feature Requests: GitHub Issues
Discussions: GitHub Discussions

License

MIT License - see LICENSE file for details

Related Projects

Model Context Protocol - Protocol specification
MCP Servers - Official MCP servers collection

Acknowledgments

This project combines functionality from various language servers and formatters. Thanks to all the maintainers of:

TypeScript, ESLint, Biome, Prettier
Pyright, gopls, rust-analyzer, ruby-lsp
And all other tools integrated into this server

Star ⭐ this repo if you find it useful!

Name		Name	Last commit message	Last commit date
src		src
.gitignore		.gitignore
.npmignore		.npmignore
.prettierrc		.prettierrc
AGENTS.md		AGENTS.md
CONTRIBUTING.md		CONTRIBUTING.md
LICENSE		LICENSE
README.md		README.md
biome.json		biome.json
bun.lock		bun.lock
eslint.config.js		eslint.config.js
package-guide.md		package-guide.md
package.json		package.json
tsconfig.json		tsconfig.json
vitest.config.ts		vitest.config.ts

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open-devtools

What is this?

Features

Supported Languages

LSP Servers (Diagnostics & Linting)

Formatters

Installation

Prerequisites

Using with Claude Desktop

Using with Cline (VS Code)

Using with Amp

Available Tools

get_diagnostics

format_file

lint_file

Configuration

LSP Configuration Structure

Formatter Configuration Structure

Available Server and Formatter Names

Configuration Examples

Disable Built-in Servers/Formatters

Override File Extensions

Add Custom LSP Server

Add Custom Formatter

Configure with Environment Variables

Multiple Configurations

How It Works

Troubleshooting

No diagnostics/linting

Formatter not found

ESLint not working

Contributing

Development Setup

Adding New LSP Servers or Formatters

Issues & Support

License

Related Projects

Acknowledgments

About

Resources

Contributing

Stars

Watchers

Forks

Releases

Packages

Contributors

Languages

`get_diagnostics`

`format_file`

`lint_file`