API & MCP

Everything a person can do on Skyfold, a program or AI agent can do with the same inputs and get the identical result.

HTTP API

• GET https://skyfold.usefulweb.app/api/v1/tools – catalog
• GET https://skyfold.usefulweb.app/api/v1/tools/{id} – inputs, output schema, examples
• POST https://skyfold.usefulweb.app/api/v1/tools/{id}/calculate – run a tool
• GET https://skyfold.usefulweb.app/api/v1/workflows · POST https://skyfold.usefulweb.app/api/v1/workflows/{id}/run
• OpenAPI 3.1: /openapi.json · /openapi.yaml
• Errors: application/problem+json; 422 includes per-field errors.

Tools on Skyfold

• Skyfold Star Map Poster – Print the real night sky of any place and moment as an SVG or PDF poster. skyfold_star_map_poster
• Skyfold Planet and Moon Positions – Where the Sun, Moon and planets are, and when they rise and set, for any place and time. skyfold_planet_positions
• Skyfold Local Eclipse Circumstances – Solar and lunar eclipses 2020–2040 as seen from your place, with contact times. skyfold_eclipse_local
• Skyfold Satellite Pass Predictor – When the ISS or any satellite flies over you, and whether you can see it, from TLE elements. skyfold_satellite_passes
• Skyfold Sun Position and Shadow Length – Sun angle and the length and direction of a shadow for any height, place and time. skyfold_sun_shadow
• Skyfold Cosmic Odometer – How far you have travelled through space since a date, frame by frame. skyfold_cosmic_odometer

Every result contains

inputs (normalised, defaults applied), summary, result (validated against the published schema), units, assumptions, sources, warnings, computedAt and links.

MCP (Model Context Protocol)

• Streamable HTTP endpoint: https://skyfold.usefulweb.app/mcp – protocol revisions 2026-07-28 (stateless) and 2025-11-25 / 2025-06-18 / 2025-03-26 (initialize handshake).
• Tools: skyfold_star_map_poster, skyfold_planet_positions, skyfold_eclipse_local, skyfold_satellite_passes, skyfold_sun_shadow, skyfold_cosmic_odometer
• Local stdio connector: node src/mcp-stdio.ts

{
  "mcpServers": {
    "usefulweb": { "type": "http", "url": "https://skyfold.usefulweb.app/mcp" }
  }
}