Skip to main content
Glama
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: 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

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

Unclaimed servers have limited discoverability.

Looking for Admin?

If you are the server author, to access and configure the admin panel.

Latest Blog Posts

MCP directory API

We provide all the information about MCP servers via our MCP API.

curl -X GET 'https://glama.ai/api/mcp/v1/servers/DrewCyber/astro-mcp'

If you have feedback or need assistance with the MCP directory API, please join our Discord server