astro-mcp
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In the chat, type
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Here is a step-by-step guide with screenshots.
astro-mcp
Astrological MCP Server — high-precision astrology tools for LLM agents.
Implements 14 tools backed by Swiss Ephemeris (pyswisseph) and integrates with any Model Context Protocol client (Claude Desktop, etc.).
Tools
# | Name | Description |
1 |
| Full natal chart: planets, angles, houses, aspects |
2 |
| Transit aspects to natal chart |
3 |
| Day-for-a-year progressions + Solar Arc |
4 |
| Annual solar return chart |
5 |
| Score candidate birth times against life events |
6 |
| Monthly lunar return chart(s) |
7 |
| Cross-chart aspects + house overlays |
8 |
| Midpoint or Davison composite chart |
9 |
| Annual profection — year lord and activated houses |
10 |
| 24 planetary hours for any day/location |
11 |
| 7 Arabic Parts (Fortune, Spirit, Marriage, etc.) |
12 |
| Planet position table over a date range |
13 |
| Find exact dates of a specific aspect |
14 |
| Antiscia and contra-antiscia points |
Related MCP server: Precision astronomical ephemeris and planetary positions via the Swiss Ephemeris.
Installation
# 1. Clone
git clone https://github.com/your-org/astro-mcp
cd astro-mcp
# 2. Create virtual environment
python3.11 -m venv .venv
source .venv/bin/activate
# 3. Install package + dev dependencies
pip install -e ".[dev]"
# 4. Download Swiss Ephemeris data files
bash scripts/download_ephe.sh
# 5. Set environment variable
export EPHE_PATH="$(pwd)/ephe"
# 6. Run tests
pytest tests/Claude Desktop configuration
Add to ~/Library/Application Support/Claude/claude_desktop_config.json:
{
"mcpServers": {
"astro": {
"command": "/path/to/astro-mcp/.venv/bin/python",
"args": ["-m", "astro_mcp"],
"env": {
"EPHE_PATH": "/path/to/astro-mcp/ephe",
"GEOCODING_PROVIDER": "nominatim",
"GEOCODING_USER_AGENT": "astro-mcp/1.0",
"LOG_LEVEL": "WARNING"
}
}
}
}Environment Variables
Variable | Default | Description |
|
| Path to Swiss Ephemeris |
|
|
|
| — | Required if |
|
| Nominatim user-agent |
|
| LRU cache size for geocoding results |
|
|
|
|
| Global orb multiplier (0.5–1.5) |
|
| Python logging level |
Architecture
src/astro_mcp/
├── server.py # MCP server — tool registration and dispatch
├── config.py # Settings from environment variables
├── core/
│ ├── models.py # Data models and astrological constants
│ ├── ephemeris_provider.py # Swiss Ephemeris wrapper (pyswisseph)
│ ├── geocoding.py # City → lat/lon/tz (geopy + timezonefinder)
│ └── formatters.py # LLM-optimized serialization
└── tools/
├── natal.py # Tool 1
├── transits.py # Tool 2
├── progressions.py # Tool 3
├── returns.py # Tools 4 + 6
├── rectification.py # Tool 5
├── synastry.py # Tools 7 + 8
├── profections.py # Tool 9
├── planetary_hours.py # Tool 10
├── arabic_parts.py # Tool 11
├── ephemeris.py # Tools 12 + 13
└── antiscia.py # Tool 14Output Format
All tools return compact JSON without whitespace to minimise LLM context tokens (~75% smaller than verbose JSON). Planet codes are abbreviated (Su, Mo, Me, etc.), aspects use 3-letter codes (Cnj, Tri, Squ), and the retrograde flag ("R":true) is omitted when direct to save additional tokens.
Planet Codes
Supported codes across tools:
SuSunMoMoonMeMercuryVeVenusMaMarsJuJupiterSaSaturnUrUranusNeNeptunePlPlutoChChironLiBlack Moon Lilith (Mean Apogee)NNNorth Node (True Node)SNSouth Node
API Notes
get_ephemerisaccepts either a singleplanetor a list of planets.get_ephemeris.stepsupports1h,2h,3h,6h,12h,1d,7d,30d.get_ephemerisnow returns atimezonefield and formatsdtinoutput_tz.find_aspect_exact_dates.modesupports:transit-to-transitfor two moving bodiestransit-to-natalfor transit to a natal planet/angleauto(default) infers mode from presence ofbirth_*
Testing
pytest tests/ -v --cov=src/astro_mcp --cov-report=term-missingReference charts (tests/reference_data/) are verified against Astro.com and Solar Fire.
License
MIT
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