OpenEphemeris — MCP Server & API Examples

Official MCP server and integration examples for Open Ephemeris — a NASA JPL DE440/DE441-backed astronomical computation engine for developers and AI agents.

MCP Server — AI Agents (Claude, Cursor, Windsurf)

Give any AI agent access to 48 typed astrological tools with zero hallucination. Powered by Swiss Ephemeris.

Quick Install — Claude Desktop/Cursor

Add to your config file:

• macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
• Windows: %APPDATA%\Claude\claude_desktop_config.json

{
  "mcpServers": {
    "openephemeris": {
      "command": "npx",
      "args": ["-y", "@openephemeris/mcp-server"],
      "env": {
        "OPENEPHEMERIS_API_KEY": "YOUR_API_KEY_HERE"
      }
    }
  }
}

Get your free API key at openephemeris.com/dashboard. Free Explorer tier — no credit card required.

Other clients — Windsurf, Zed, etc.

See SETUP.md for platform-specific walkthroughs.

What you can ask

"Calculate a natal chart for 1990-04-15 at 2:30 PM in Chicago."
"Find all Saturn transits to my natal Sun in the next 6 months."
"Get the current moon phase and void-of-course status."
"Find the next solar eclipse visible from Tokyo."
"Find the best electional window to sign a contract in March."
"Generate a Human Design chart for my birth data."
"What is my Vedic (sidereal) chart?"
"Calculate my Chinese BaZi (Four Pillars) chart."
"Show me my Astrocartography power lines — where is my Venus line?"
"Calculate a synastry chart between two people."
"Find the next Venus Star Point and my relationship to it."
"What planetary stations are coming in the next 3 months?"

Tools at a glance

Full npm package: @openephemeris/mcp-server

REST API Examples

Ready-to-run scripts for interacting with the OpenEphemeris API directly.

Repository structure

Quick start

# 1. Get a free API key
open https://openephemeris.com/dashboard

# 2. Try the API
curl -H "Authorization: Bearer YOUR_KEY" \
  "https://api.openephemeris.com/ephemeris/moon/phase"

# 3. Run a Python example
cd python && pip install requests && python natal_chart.py

Why OpenEphemeris?

Most LLMs hallucinate astronomical data — planets, degrees, house positions. OpenEphemeris connects AI agents directly to the math.

• Zero-hallucination accuracy — sub-arcsecond precision from NASA JPL DE440/DE441
• LLM-optimized output — format=llm compresses chart responses by ~50%, cutting inference costs
• 111 REST endpoints across 6 tiers, starting free
• 48 typed MCP tools — natal, Human Design, Vedic, BaZi, astrocartography, electional, Venus cycles, and more

Links