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DrewCyber

astro-mcp

by DrewCyber

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

calculate_natal_chart

Full natal chart: planets, angles, houses, aspects

2

calculate_transits

Transit aspects to natal chart

3

calculate_secondary_progressions

Day-for-a-year progressions + Solar Arc

4

calculate_solar_return

Annual solar return chart

5

calculate_rectification_hints

Score candidate birth times against life events

6

calculate_lunar_return

Monthly lunar return chart(s)

7

calculate_synastry

Cross-chart aspects + house overlays

8

calculate_composite_chart

Midpoint or Davison composite chart

9

calculate_profections

Annual profection — year lord and activated houses

10

get_planetary_hours

24 planetary hours for any day/location

11

calculate_arabic_parts

7 Arabic Parts (Fortune, Spirit, Marriage, etc.)

12

get_ephemeris

Planet position table over a date range

13

find_aspect_exact_dates

Find exact dates of a specific aspect

14

calculate_antiscia

Antiscia and contra-antiscia points

Related MCP server: auseklis

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

EPHE_PATH

./ephe

Path to Swiss Ephemeris .se1 data files

GEOCODING_PROVIDER

nominatim

nominatim or opencage

OPENCAGE_API_KEY

Required if GEOCODING_PROVIDER=opencage

GEOCODING_USER_AGENT

astro-mcp/1.0

Nominatim user-agent

GEOCODE_CACHE_SIZE

512

LRU cache size for geocoding results

DEFAULT_HOUSE_SYSTEM

P

P=Placidus, W=Whole Sign, K=Koch

DEFAULT_ORB_FACTOR

1.0

Global orb multiplier (0.5–1.5)

LOG_LEVEL

WARNING

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 14

Output 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:

  • Su Sun

  • Mo Moon

  • Me Mercury

  • Ve Venus

  • Ma Mars

  • Ju Jupiter

  • Sa Saturn

  • Ur Uranus

  • Ne Neptune

  • Pl Pluto

  • Ch Chiron

  • Li Black Moon Lilith (Mean Apogee)

  • NN North Node (True Node)

  • SN South Node

API Notes

  • get_ephemeris accepts either a single planet or a list of planets.

  • get_ephemeris.step supports 1h, 2h, 3h, 6h, 12h, 1d, 7d, 30d.

  • get_ephemeris now returns a timezone field and formats dt in output_tz.

  • find_aspect_exact_dates.mode supports:

    • transit-to-transit for two moving bodies

    • transit-to-natal for transit to a natal planet/angle

    • auto (default) infers mode from presence of birth_*

Testing

pytest tests/ -v --cov=src/astro_mcp --cov-report=term-missing

Reference charts (tests/reference_data/) are verified against Astro.com and Solar Fire.

License

MIT

A
license - permissive license
-
quality - not tested
C
maintenance

Maintenance

Maintainers
Response time
Release cycle
Releases (12mo)
Commit activity

Resources

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