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Ephemeris MCP

Calculates Tropical Zodiac positions for planets, luminaries, and chart angles from time and observer coordinates.

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Install Ephemeris MCP

Pick your client, then add it in one click or paste the config.

STDIOPython
~/Library/Application Support/Claude/claude_desktop_config.json
claude_desktop_config.json
{
  "mcpServers": {
    "ephemeris-mcp": {
      "command": "uvx",
      "args": [
        "ephemeris-mcp"
      ]
    }
  }
}

Settings → Developer → Edit Config, merge this into mcpServers, then fully quit and reopen Claude Desktop.

We couldn’t confirm it starts correctly

We ran the install command but it didn't respond within our test window — this can mean a slow first-time install rather than a real problem.

uvx ephemeris-mcp

Process exited before answering initialize.

This is an experimental automated check and can have false negatives — missing environment variables, a slow cold install, etc. It doesn’t necessarily mean something’s wrong. Last checked 6d ago.

Overview

The ephemeris-mcp MCP server calculates precise planetary positions through the Swiss Ephemeris. Its get_planetary_positions tool accepts an ISO-8601 timestamp plus latitude and longitude, then returns Tropical Zodiac data for the Sun, Moon, planets, Ascendant, and Midheaven. Use it when an agent needs astronomical or astrological position data tied to a specific time and location. It runs as a standard stdin/stdout MCP process through uvx, pip, or Docker.

Use cases

  • Calculate planetary positions for a specified timestamp
  • Generate Tropical Zodiac data for an observer location
  • Retrieve Ascendant and Midheaven values
  • Provide structured motion and declination data to an AI agent

Key features

  • Swiss Ephemeris calculations
  • Tropical Zodiac positions
  • ISO-8601 timestamp input
  • Latitude and longitude parameters
  • Planet, Sun, and Moon data
  • Ascendant and Midheaven output

Tools1

What Ephemeris MCP lets your agent do. Expand a tool for its parameters.

Self-reported~28 tokens of context

Security & health

What it can reach and how reliably it runs — from our own checks, not the maintainer’s claims.

ActiveLast checked Today

Recent health check succeeded.

5/5 checks healthy over the last 45d

Supply-chain signal

No high-severity advisories surfaced by our automated scan.

Critical 0High 0Medium 0Low 0

Scanned 9d ago via OSV.dev · ephemeris-mcp (PyPI)

Adoption & maintenance

Factual signals from GitHub, npm, and our automated checks — not a rating.

GitHub stars4Stargazers on the source repository.
Last commit7mo agoMost recent push to the default branch.
Install checkInconclusiveDidn't respond in our test window — often a slow first install.
Tools exposed1Callable tools this server registers over MCP.
Directory activity2 viewsConfig copies, upvotes, and views on AllMCPs.

How Ephemeris MCP works

What ephemeris-mcp MCP server does

ephemeris-mcp MCP server exposes Swiss Ephemeris calculations to MCP-compatible AI clients. It focuses on position data rather than general astronomy workflows: one available tool calculates Tropical Zodiac placements for the Sun, Moon, planets, and chart angles.

The result includes a bodies collection with each body's sign, degree, apparent motion direction, speed, and declination. A separate houses collection reports the Ascendant (ASC) and Midheaven (MC), including their signs and degrees. This makes the server suitable for agents that need to retrieve chart-related positions from a timestamp and observing location.

How it works

Call get_planetary_positions with an ISO-8601 timestamp such as 2025-12-16T15:28:00Z. Supply the observer's latitude and longitude as floating-point values when the calculation should use a location other than the defaults. The documented defaults are 42.3314 latitude and -83.0458 longitude, corresponding to Detroit, Michigan.

The MCP client starts the server as a subprocess and exchanges messages over standard input and output. Once the client no longer needs the process, it can terminate it. The calculation engine uses the Swiss Ephemeris, while the returned coordinate system is geocentric Tropical Ecliptic according to the project's architecture notes.

Setup and configuration

The recommended package-based setup runs the server with uvx, which avoids a separate local installation:

bash
uvx ephemeris-mcp

A global pip installation is also documented:

Terminal
pip install ephemeris-mcp
python -m ephemeris_mcp

Register the executable in the MCP client's server configuration with uvx as the command and ephemeris-mcp as its argument. Docker is an alternative when container isolation is preferred. The published image is ghcr.io/scottchronicity/ephemeris-mcp:latest; the documented client configuration runs it with docker run --rm -i.

For development, the repository uses uv sync, uv run ephemeris-mcp, and a Makefile for tests and validation. No environment variables are specified in the available setup instructions.

Tools and capabilities

The server currently documents one tool:

  • get_planetary_positions: Calculates Tropical Zodiac positions for the Sun, Moon, planets, and chart angles from an ISO-8601 time and observer coordinates.

Its response provides body-level sign, degree, motion, speed, and declination fields, plus Ascendant and Midheaven data. ephemeris-mcp MCP server therefore fits requests that need structured position output, rather than a broad collection of ephemeris queries or mutation operations.

Limitations and notes

Latitude and longitude affect the location-dependent chart angles, and omitted coordinates fall back to the documented Detroit defaults. The project is licensed under AGPLv3, so review that license before embedding or distributing the server in a larger application.

Read the full README View source on GitHub

Reviews

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Frequently Asked Questions about Ephemeris MCP

ephemeris-mcp is an MCP server that connects AI agents to the Swiss Ephemeris for precision astronomical calculations. Its main tool, get_planetary_positions, accepts an ISO-8601 time and observer coordinates, then returns Tropical Zodiac positions for the Sun, Moon, planets, Ascendant, and Midheaven.

Install it with `uvx ephemeris-mcp` or with `pip install ephemeris-mcp`. You can also run the published Docker image, `ghcr.io/scottchronicity/ephemeris-mcp:latest`, with an interactive stdin connection.

Register `uvx` as the command and `ephemeris-mcp` as its argument so the client can start the standard stdin/stdout server.

The tool needs an ISO-8601 timestamp and accepts latitude and longitude as floating-point observer coordinates. If coordinates are omitted, the documented defaults are Detroit, Michigan: 42.3314 latitude and -83.0458 longitude.

Run `docker run --rm -i ghcr.io/scottchronicity/ephemeris-mcp:latest` and use the same command and arguments in the MCP client configuration. The `--rm` option removes the container after it exits.

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