Malloy MCP Server

An MCP server implementation for executing Malloy queries and managing Malloy resources.

Features

• Execute Malloy queries via MCP
• Access Malloy project, package, and model metadata
• Robust error handling with detailed context
• Comprehensive test coverage
• Type-safe implementation

Installation

# Install using uv (recommended)
uv pip install malloy-mcp-server

# Or using pip
pip install malloy-mcp-server

Usage

Starting the Server

from malloy_mcp_server import mcp

# Run the server
if __name__ == "__main__":
    mcp.serve()

Configuration

The server can be configured using environment variables:

Variable	Description	Default
MALLOY_PUBLISHER_ROOT_URL	URL of the Malloy Publisher API	http://localhost:4000

Example:

# Set the publisher URL
export MALLOY_PUBLISHER_ROOT_URL="http://malloy-publisher:4000"

# Run with custom configuration
python -m malloy_mcp_server

Executing Queries

The server provides an MCP tool for executing Malloy queries:

from malloy_mcp_server import ExecuteMalloyQueryTool

# Example query execution
result = await ExecuteMalloyQueryTool(
    query="select * from users",
    model_path="my_package/users"
)

Accessing Resources

The server provides the following resource endpoints:

• malloy://project/home/metadata - Project metadata
• malloy://project/home/package/{package_name} - Package metadata
• malloy://project/home/model/{model_path} - Model metadata

Development

Setup

1. Clone the repository:

git clone https://github.com/namabile/malloy-mcp-server.git
cd malloy-mcp-server

2. Install dependencies:

uv pip install -e ".[dev]"

Running Tests

# Run all tests
pytest

# Run with coverage
pytest --cov=malloy_mcp_server

Code Quality

The project uses:

• black for code formatting
• mypy for type checking
• ruff for linting

Run quality checks:

black .
mypy .
ruff check .

Error Handling

The server provides detailed error handling with context:

from malloy_mcp_server.errors import QueryExecutionError

try:
    result = await ExecuteMalloyQueryTool(...)
except QueryExecutionError as e:
    print(f"Error: {e.message}")
    print("Context:", e.context)

Architecture

The server is built on:

• FastMCP for the MCP server implementation
• Malloy Publisher Client for Malloy interactions
• Pydantic for data validation

Key components:

• server.py - Core server implementation
• tools/query_executor.py - Query execution tool
• errors.py - Error handling utilities

Contributing

1. Fork the repository
2. Create a feature branch
3. Make your changes
4. Add tests for new functionality
5. Submit a pull request

License

MIT License - see LICENSE file for details