Open Ephemeris is a production-grade MCP server that gives Claude, ChatGPT, Gemini, Cursor, and any MCP-compatible agent direct access to real astronomical data. Over 100 tools cover the full range of astrological traditions: natal chart calculation, transit and progression forecasting, synastry, astrocartography ACG lines, Human Design body graph, BaZi four pillars, eclipse windows, lunar phases, planetary hours, and fixed star positions. All positions are computed at request time from JPL DE440 — accurate to arc-second precision. No hallucinated positions. No astronomy math in your application code. Free tier available.
Overview
Open Ephemeris is a high-precision astrology API with an MCP server exposing 116+ endpoints across natal charts, transits, synastry, Human Design, BaZi, solar returns, and more.
Calculated using the JPL DE440 ephemeris. Supports Claude, ChatGPT, and Gemini CLI.
Features:
- Natal chart positions, houses, and aspects
- Transit forecasting and ingress tracking
- Synastry and composite charts
- Human Design bodygraph
- BaZi four pillars
- Moon phases, eclipses, retrograde cycles
Get an API key at openephemeris.com
Server Config
{
"mcpServers": {
"openephemeris": {
"command": "npx",
"args": [
"-y",
"@openephemeris/mcp-server"
],
"env": {
"OPENEPHEMERIS_API_KEY": "YOUR_API_KEY"
}
}
}
}