# CycleCalcs

**Canonical:** https://apis.io/providers/cyclecalcs/  
**Website:** https://www.cyclecalcs.com/api.html  
**APIs profiled:** 30

CycleCalcs publishes a read-only positional-astronomy engine as both a REST API and a hosted MCP server over the same core: sun and moon rise/set and twilight, moon phases and libration, planet positions and a visibility board, eclipses with per-observer local circumstances, seasons, apsides, lunar nodes, retrograde stations, conjunctions and angular separation, sidereal time, the equation of time, Jupiter's Galilean moons, sky quality and dark-sky windows, place lookup, and a one-call whole-sky snapshot. It returns the named answer and the numbers behind it rather than raw ephemeris, and every response states its frame, epoch, time scale and refraction model. Computed live with the MIT-licensed Astronomy Engine, arcminute class for the Sun, Moon and planets from 1700 to 2200. Twenty-nine GET endpoints, JSON/CSV/TXT, RFC 9457 problem documents, open CORS, and a free tier that needs no key, no signup and no card; paid volume tiers sell through RapidAPI. Pure astronomy — no astrology and no claims that sky events affect people or Earth.

## Kin Score — 62.4 / 100 (strong)

Scored 2026-08-12 under rubric 0.11.0. Trend: flat (+0.0 from 62.4).

| Facet | Score |
|---|---|
| Discoverability | 81.5 |
| Contract Quality | 65.5 |
| Governance | 31.3 |
| Operational Transparency | 55.3 |
| Developer Ergonomics | 58.2 |
| Commercial Clarity | 76.3 |

## Agent readiness — 52.5 (agent-native)

| Dimension | Value |
|---|---|
| Spec Presence | yes |
| Agentic Access | derived |
| MCP Server | no |
| Auth Clarity | yes |
| Idempotency | documented |
| Error Semantics | verified |
| OpenAPI Examples | verified |
| Rate Limit Signal | verified |
| Event Surface Described | no |
| Agent Skills | derived |
| Well Known Catalog | no |
| Consent Identity | no |
| Agent Card | no |
| Dry Run Mode | no |

## APIs (30)

- **CycleCalcs MCP Server** — Hosted stateless Streamable HTTP MCP server exposing 11 astronomy tools backed by the v2 REST endpoints. Requires Bearer RapidAPI key on every call; basic plan free. Works with ...
- **CycleCalcs Apsides API** — The Apsides API from CycleCalcs — 1 operation(s) for apsides.
- **CycleCalcs Attribution API** — The Attribution API from CycleCalcs — 1 operation(s) for attribution.
- **CycleCalcs Conjunctions API** — The Conjunctions API from CycleCalcs — 1 operation(s) for conjunctions.
- **CycleCalcs Conventions API** — The Conventions API from CycleCalcs — 1 operation(s) for conventions.
- **CycleCalcs CycleCalcs Astronomy API API** — The CycleCalcs Astronomy API API from CycleCalcs — 1 operation(s) for cyclecalcs astronomy api.
- **CycleCalcs Cycles API** — The Cycles API from CycleCalcs — 1 operation(s) for cycles.
- **CycleCalcs Dark Window API** — The Dark Window API from CycleCalcs — 1 operation(s) for dark window.
- **CycleCalcs Eclipses API** — The Eclipses API from CycleCalcs — 1 operation(s) for eclipses.
- **CycleCalcs Enums API** — The Enums API from CycleCalcs — 1 operation(s) for enums.
- **CycleCalcs Equation Of Time API** — The Equation Of Time API from CycleCalcs — 1 operation(s) for equation of time.
- **CycleCalcs Jupiter Moons API** — The Jupiter Moons API from CycleCalcs — 1 operation(s) for jupiter moons.
- **CycleCalcs Libration API** — The Libration API from CycleCalcs — 1 operation(s) for libration.
- **CycleCalcs Moon API** — The Moon API from CycleCalcs — 1 operation(s) for moon.
- **CycleCalcs Moon Nodes API** — The Moon Nodes API from CycleCalcs — 1 operation(s) for moon nodes.
- **CycleCalcs Phases API** — The Phases API from CycleCalcs — 1 operation(s) for phases.
- **CycleCalcs Places API** — The Places API from CycleCalcs — 1 operation(s) for places.
- **CycleCalcs Planet Board API** — The Planet Board API from CycleCalcs — 1 operation(s) for planet board.
- **CycleCalcs Planet Events API** — The Planet Events API from CycleCalcs — 1 operation(s) for planet events.
- **CycleCalcs Positions API** — The Positions API from CycleCalcs — 1 operation(s) for positions.
- **CycleCalcs Retrogrades API** — The Retrogrades API from CycleCalcs — 1 operation(s) for retrogrades.
- **CycleCalcs Rise Set API** — The Rise Set API from CycleCalcs — 1 operation(s) for rise set.
- **CycleCalcs Seasons API** — The Seasons API from CycleCalcs — 1 operation(s) for seasons.
- **CycleCalcs Separation API** — The Separation API from CycleCalcs — 1 operation(s) for separation.
- **CycleCalcs Sidereal Time API** — The Sidereal Time API from CycleCalcs — 1 operation(s) for sidereal time.
- **CycleCalcs Sky Quality API** — The Sky Quality API from CycleCalcs — 1 operation(s) for sky quality.
- **CycleCalcs Sun API** — The Sun API from CycleCalcs — 1 operation(s) for sun.
- **CycleCalcs Time API** — The Time API from CycleCalcs — 1 operation(s) for time.
- **CycleCalcs Today API** — The Today API from CycleCalcs — 1 operation(s) for today.
- **CycleCalcs Twilight API** — The Twilight API from CycleCalcs — 1 operation(s) for twilight.

## MCP servers (2)

- **mcp**
- **MCP server manifest (11 tools, captured from tools/list)**

## Agentic access (1)

- **Cyclecalcs Agentic Access** — 29 operations

## Security (2)

- **Cyclecalcs Authentication** — none/apiKey · 4 schemes
- **Cyclecalcs Domain Security** — TLSv1.3 · HSTS · DNSSEC · DMARC

## Plans (1)

- **Cyclecalcs Plans**

## Tags

Astronomy, Space, Science, Ephemeris, Sun, Moon, Planets, Eclipses, Time, Calendar, Geolocation, MCP, Agent-native

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Profiled by [API Evangelist](https://apievangelist.com) and published on [APIs.io](https://apis.io/providers/cyclecalcs/). Scores are computed from the provider's own public artifacts under a published rubric.