Cromwell MCP Server

Execute scientific workflows written in WDL using Cromwell engine with MCP integration for AI-assisted genomics pipeline orchestration.

What is Cromwell MCP?

Cromwell MCP is a Model Context Protocol server implementation that brings Cromwell capabilities directly into AI-powered development workflows. By connecting Cromwell's powerful workflow features to MCP-compatible clients like Claude Desktop, VS Code, and other AI assistants, developers can leverage intelligent automation for their workflow projects.

The Model Context Protocol (MCP) is an open standard developed by Anthropic that enables AI models to securely interact with external tools and data sources. Cromwell MCP implements this protocol specifically for Cromwell, allowing seamless integration between AI assistants and Cromwell's extensive feature set.

Whether you're building production applications, prototyping new ideas, or managing complex workflow infrastructure, Cromwell MCP provides the bridge between AI intelligence and Cromwell's practical capabilities. This integration enables developers to work faster, make better decisions, and automate repetitive tasks in their workflow workflows.

Key Features and Capabilities

AI-Powered Automation

Automate complex Cromwell workflows through natural language commands and AI-driven task execution.

Real-time Integration

Connect Cromwell directly to AI assistants for live interaction with your workflow projects.

Secure Protocol

Built on MCP's secure communication standard with proper authentication and access control.

Extensible Architecture

Modular design allows custom extensions and plugins to expand Cromwell integration capabilities.

Cromwell MCP exposes a comprehensive set of tools through the MCP protocol that enable AI assistants to interact with Cromwell in meaningful ways. These tools cover the full spectrum of Cromwell's functionality, from basic operations to advanced configuration and management tasks.

The server handles all communication between the AI client and Cromwell, translating natural language requests into specific Cromwell API calls and returning structured results that the AI can interpret and present to the user. This abstraction layer means developers don't need to memorize complex API documentation — they can simply describe what they want to accomplish.

Installation and Setup

Prerequisites

Before installing Cromwell MCP, ensure your development environment meets the following requirements:

Quick Installation

Install Cromwell MCP globally using npm for the fastest setup:

npm install -g cromwell-mcp

# Verify installation
cromwell-mcp --version

# Start the server
cromwell-mcp start

Configuration with Claude Desktop

Add the following configuration to your Claude Desktop settings file (claude_desktop_config.json):

{
  "mcpServers": {
    "cromwell-mcp": {
      "command": "npx",
      "args": ["-y", "cromwell-mcp"],
      "env": {
        "API_KEY": "your-api-key-here"
      }
    }
  }
}

Docker Installation

For containerized deployments, use the Docker image:

# Pull the image
docker pull reaking/cromwell-mcp:latest

# Run the container
docker run -d \
  --name cromwell-mcp \
  -p 3000:3000 \
  -e API_KEY=your-api-key \
  reaking/cromwell-mcp:latest

Architecture and Design

Cromwell MCP follows a modular architecture designed for reliability, performance, and extensibility. The server consists of several key components that work together to provide seamless Cromwell integration through the MCP protocol.

Server Components

The core architecture includes the following layers:

  1. MCP Protocol Handler: Manages the JSON-RPC communication between AI clients and the server, handling request routing, response formatting, and error management.
  2. Cromwell Integration Layer: Provides the bridge between MCP tool calls and Cromwell's native API, translating requests into appropriate Cromwell operations.
  3. Authentication Module: Handles API key validation, token management, and access control to ensure secure interactions with Cromwell resources.
  4. Caching System: Implements intelligent caching of frequently accessed data to minimize API calls and improve response times.
  5. Event System: Monitors Cromwell events and state changes, enabling reactive workflows and real-time notifications.

Communication Flow

When a user makes a request through their AI assistant, the following flow occurs:

  1. The AI client sends an MCP tool call request via JSON-RPC over stdio or SSE transport
  2. The protocol handler validates the request and routes it to the appropriate tool implementation
  3. The Cromwell integration layer executes the requested operation against the Cromwell API or local instance
  4. Results are formatted according to MCP response specifications and returned to the AI client
  5. The AI assistant interprets the results and presents them to the user in a meaningful way

Available Tools and Functions

Cromwell MCP exposes a rich set of tools through the MCP protocol. Each tool is designed for a specific aspect of Cromwell interaction and can be invoked by AI assistants through natural language.

Core Tools

Advanced Tools

Use Cases and Applications

Enterprise Development Teams

Large development teams benefit from Cromwell MCP by standardizing their Cromwell workflows through AI assistance. Team members can use natural language to perform complex operations without deep expertise in every aspect of Cromwell, reducing onboarding time and improving consistency across projects.

The MCP integration enables team leads to create standardized workflows that AI assistants can execute, ensuring best practices are followed across all projects. This is particularly valuable for organizations with multiple teams working on different workflow projects simultaneously.

Rapid Prototyping

Developers building proof-of-concept applications can use Cromwell MCP to dramatically accelerate their prototyping process. Instead of spending time reading documentation and configuring tools manually, they can describe their desired outcome and let the AI assistant handle the implementation details.

DevOps and CI/CD Integration

Cromwell MCP integrates seamlessly with existing DevOps pipelines. The MCP server can be called from CI/CD scripts to perform automated tasks like building, testing, and deploying Cromwell applications. This enables intelligent pipeline automation that adapts to project requirements and code changes.

Learning and Education

For developers new to Cromwell, Cromwell MCP serves as an interactive learning companion. The AI assistant can explain concepts, demonstrate best practices, and guide users through complex operations step by step, making the learning curve significantly less steep.

Configuration Reference

Environment Variables

Configure Cromwell MCP using the following environment variables:

# Required settings
API_KEY=your-cromwell-mcp-api-key
SERVER_PORT=3000

# Optional settings
LOG_LEVEL=info
CACHE_TTL=3600
MAX_CONNECTIONS=10
TIMEOUT=30000
RETRY_ATTEMPTS=3

# Cromwell-specific settings
CROMWELL_MCP_HOME=/path/to/cromwell-mcp
CROMWELL_MCP_CONFIG=/path/to/config

Advanced Configuration

For advanced deployments, create a configuration file at ~/.cromwell-mcp/config.json:

{
  "server": {
    "port": 3000,
    "host": "localhost",
    "transport": "stdio"
  },
  "auth": {
    "type": "api-key",
    "required": true
  },
  "logging": {
    "level": "info",
    "format": "json",
    "output": "stdout"
  },
  "cache": {
    "enabled": true,
    "ttl": 3600,
    "maxSize": "100mb"
  },
  "cromwell": {
    "version": "latest",
    "autoUpdate": false,
    "plugins": []
  }
}

Best Practices

Security Considerations

Performance Optimization

Development Workflow

Troubleshooting

Common Issues

Connection refused errors: Ensure the MCP server is running and the configured port is not blocked by a firewall. Check that your MCP client configuration points to the correct server address and port.

Authentication failures: Verify that your API key is correctly set in the environment variables. Check for trailing whitespace or newline characters in the key value. Ensure the API key has the required permissions for the operations you're attempting.

Timeout errors: Increase the timeout configuration for operations that process large amounts of data. Consider enabling caching to reduce the time for repeated requests. Check network latency between the client and server.

Tool not found errors: Ensure you're running the latest version of Cromwell MCP. Some tools may require additional plugins or dependencies. Run cromwell-mcp --list-tools to see all available tools in your installation.

Debug Mode

Enable debug logging for detailed troubleshooting information:

# Enable debug mode
LOG_LEVEL=debug cromwell-mcp start

# Or set in your configuration
export CROMWELL_MCP_DEBUG=true

Comparison with Alternatives

Cromwell MCP stands out in the workflow MCP ecosystem for several reasons. While other solutions may offer similar basic functionality, Cromwell MCP provides deeper Cromwell integration, better performance characteristics, and a more comprehensive toolset.

Key differentiators include native support for Cromwell's latest features, optimized caching strategies for workflow operations, and a plugin system that allows the community to extend functionality. The server also benefits from active development and regular updates aligned with both MCP protocol evolution and Cromwell releases.

When choosing between MCP servers for workflow work, consider factors like the specific Cromwell features you need, your deployment environment, performance requirements, and the level of customization your project demands. Cromwell MCP is particularly well-suited for teams that want deep Cromwell integration with minimal configuration overhead.

Community and Support

The Cromwell MCP project is supported by an active community of developers who contribute to its development, documentation, and ecosystem. Here are the key resources for getting help and staying connected:

Frequently Asked Questions

Is Cromwell MCP free to use?

Cromwell MCP is available as an open-source project with a permissive license. Basic functionality is completely free, while some advanced features may require a Cromwell API key or subscription depending on the specific tools used.

Which MCP clients are compatible?

Cromwell MCP works with any MCP-compatible client, including Claude Desktop, VS Code with the MCP extension, Cursor, Windsurf, and other AI development tools that support the Model Context Protocol standard.

Can I self-host Cromwell MCP?

Yes, Cromwell MCP can be self-hosted on any server that supports Node.js. Docker images are provided for easy deployment, and the server can be configured to run behind a reverse proxy for production environments.

How often is Cromwell MCP updated?

The project follows a regular release schedule with minor updates every two weeks and major releases quarterly. Security patches are released as needed. Subscribe to the GitHub repository for release notifications.

Does Cromwell MCP support multiple languages?

While Cromwell MCP is primarily designed for Cromwell development, the MCP protocol support enables interaction with any AI assistant regardless of the language used for prompts. The server responds in the language of the request.

Getting Started Tutorial

Follow this step-by-step tutorial to get up and running with Cromwell MCP in under 10 minutes:

  1. Install the server: Run npm install -g cromwell-mcp to install globally
  2. Configure your client: Add the MCP server configuration to your AI assistant's settings
  3. Set up authentication: Create an API key and set it in your environment variables
  4. Test the connection: Ask your AI assistant to list available Cromwell tools
  5. Start building: Use natural language to create your first Cromwell project through the AI assistant

Once you've completed the basic setup, explore the advanced configuration options and additional tools to customize Cromwell MCP for your specific workflow needs. The community documentation includes extensive examples and use cases to help you get the most out of the integration.