Precision Astronomical Ephemeris And Planetary Positions Via The Swiss Ephemeris.

PyPI version CI License: AGPL v3

mcp-name: io.github.scottchronicity/ephemeris-mcp

Precision Astronomical Ephemeris for AI Agents.

Ephemeris MCP is a Model Context Protocol (MCP) server that provides AI agents with precision planetary positions using the Swiss Ephemeris.

To use this in Claude Desktop, add this to your claude_desktop_config.json:

"mcpServers": {
  "ephemeris": {
    "command": "uvx",
    "args": ["ephemeris-mcp"]
  }
}

Quick Start

Install via PyPI (Recommended)

# Install with uvx (recommended - fast & isolated, no local install needed)
uvx ephemeris-mcp

# Or install globally with pip
pip install ephemeris-mcp
python -m ephemeris_mcp

Register with MCP Clients

Add to your MCP client configuration (client will start server on-demand):

Claude Desktop (~/Library/Application Support/Claude/claude_desktop_config.json):

{
  "mcpServers": {
    "ephemeris-mcp": {
      "command": "uvx",
      "args": ["ephemeris-mcp"]
    }
  }
}

VS Code/Cursor/Windsurf (Cline MCP settings):

{
  "mcpServers": {
    "ephemeris-mcp": {
      "command": "uvx",
      "args": ["ephemeris-mcp"]
    }
  }
}

The client starts the server process automatically, communicates over stdin/stdout, then terminates it when done.

Alternative: Docker

If you prefer container isolation:

# Pull latest image
docker pull ghcr.io/scottchronicity/ephemeris-mcp:latest

# Test it
docker run --rm -i ghcr.io/scottchronicity/ephemeris-mcp:latest

Configure MCP client with Docker:

{
  "mcpServers": {
    "ephemeris-mcp": {
      "command": "docker",
      "args": ["run", "--rm", "-i", "ghcr.io/scottchronicity/ephemeris-mcp:latest"]
    }
  }
}

Local Development

# Clone and install
git clone https://github.com/scottchronicity/ephemeris-mcp.git
cd ephemeris-mcp
uv sync

# Run tests
make test

# Run locally
uv run ephemeris-mcp

# Test the engine directly
make validate-happycase

Available Tools

get_planetary_positions

Returns precise Tropical Zodiac positions for all planets, Sun, Moon, and chart angles.

Parameters:

• iso_time (string): ISO-8601 timestamp (e.g., "2025-12-16T15:28:00Z")
• latitude (float): Observer latitude (default: 42.3314 - Detroit, MI)
• longitude (float): Observer longitude (default: -83.0458 - Detroit, MI)

Returns:

• bodies: Sun, Moon, planets with sign, degrees, motion (direct/retrograde), speed, declination
• houses: Ascendant (ASC) and Midheaven (MC) with sign and degrees

Architecture

See docs/adr/ for architectural decisions:

• ADR 001: Geocentric Tropical Ecliptic coordinates specification
• ADR 002: Semantic versioning with Conventional Commits
• ADR 003: CI/CD pipeline architecture

License

AGPLv3