Open Ephemeris MCP server

OpenEphemeris MCP Server

Model Context Protocol server for OpenEphemeris — typed astrology tools powered by the NASA JPL DE440 ephemeris. Zero hallucination on planetary positions, dates, and degrees. Covers 1,100 years of astronomical data.

Hosted endpoint: https://mcp.openephemeris.com/mcp (Streamable HTTP, MCP 2025-11-25 spec)

Quick Start

Install via Smithery (recommended)

The fastest way to connect any MCP-compatible client:

npx -y @smithery/cli install @open-ephemeris/openephemeris --client claude

Or browse the listing and copy connection snippets: smithery.ai/servers/open-ephemeris/openephemeris

Connect via AI SDK (Vercel AI SDK)

import Smithery from "@smithery/api"
import { createMCPClient } from "@ai-sdk/mcp"
import { generateText } from "ai"
import { anthropic } from "@ai-sdk/anthropic"
import { createConnection } from "@smithery/api/mcp"

const smithery = new Smithery()

const conn = await smithery.connections.create("{your-namespace}", {
  mcpUrl: "https://server.smithery.ai/open-ephemeris/openephemeris",
  headers: {
    apiKey: "your-openephemeris-api-key", // get one free at openephemeris.com/dashboard
  },
})

const { transport } = await createConnection({
  client: smithery,
  namespace: "{your-namespace}",
  connectionId: conn.connectionId,
})

const mcpClient = await createMCPClient({ transport })
const tools = await mcpClient.tools()

const { text } = await generateText({
  model: anthropic("claude-sonnet-4-20250514"),
  tools,
  prompt: "Calculate a natal chart for someone born April 15, 1990 at 2:30 PM in Chicago.",
})

await mcpClient.close()

Connect via MCP SDK (TypeScript)

import Smithery from "@smithery/api"
import { Client } from "@modelcontextprotocol/sdk/client/index.js"
import { createConnection } from "@smithery/api/mcp"

const smithery = new Smithery()

const conn = await smithery.connections.create("{your-namespace}", {
  mcpUrl: "https://server.smithery.ai/open-ephemeris/openephemeris",
  headers: {
    apiKey: "your-openephemeris-api-key",
  },
})

const { transport } = await createConnection({
  client: smithery,
  namespace: "{your-namespace}",
  connectionId: conn.connectionId,
})

const mcpClient = new Client(
  { name: "my-app", version: "1.0.0" },
  { capabilities: {} }
)
await mcpClient.connect(transport)

const { tools } = await mcpClient.listTools()
const result = await mcpClient.callTool({
  name: "ephemeris_natal_chart",
  // A datetime that states a clock time must state its zone: either pass
  // `timezone` alongside the local time, or put a Z/±HH:MM offset on the value.
  arguments: {
    datetime: "1990-04-15T14:30:00",
    timezone: "America/Chicago",
    latitude: 41.8781,
    longitude: -87.6298,
    format: "llm",
  },
})

Connect directly (Streamable HTTP, no Smithery)

Shortened. The full README is on GitHub.