generated: '2026-08-09'
method: searched
status: published
source: https://www.cyclecalcs.com/api/mcp.html
description: >-
  CycleCalcs publishes a hosted, stateless Streamable HTTP MCP server that
  exposes eleven read-only astronomy tools, each backed by exactly one live
  /v2 REST endpoint. The server speaks MCP revision 2026-07-28 and the earlier
  2025 handshake revisions. `initialize` and `tools/list` are answered
  anonymously — the full eleven-tool manifest, with input AND output JSON
  Schemas, is readable without a key — and only `tools/call` requires one.
server:
  name: cyclecalcs
  transport: http           # Streamable HTTP, POST only, JSON responses
  url: https://www.cyclecalcs.com/mcp
  protocol_revisions:
    - '2026-07-28'
    - '2025 handshake revisions (backwards compatible)'
  stateless: true
  docs: https://www.cyclecalcs.com/api/mcp.html
authentication:
  browsing: none            # initialize + tools/list are anonymous
  invocation: required
  headers:
    - name: Authorization
      form: Bearer <RapidAPI key>
    - name: X-Api-Key
      form: raw key, no Bearer prefix
  key_source: https://rapidapi.com/info-8KZIhinZ9/api/cyclecalcs-astronomy-api3
  free_tier: Basic plan is free
  refusal_behavior: >-
    A tool call without a key is refused as a normal tool result carrying
    instructions, not as an HTTP 401 that would drop the connection.
  notes: >-
    Cannot currently be added to ChatGPT connectors, which authenticate with
    OAuth or not at all. The OpenAI Responses API can attach it today by
    passing the key in the mcp tool's `authorization` field.
clients:
  - name: Claude Code
    install: >-
      claude mcp add --transport http cyclecalcs https://www.cyclecalcs.com/mcp
      --header "Authorization: Bearer YOUR_KEY"
  - name: Claude web/desktop
    install: Custom connector with the server URL and an Authorization header
tool_count: 11
tools:
  - name: astro_sky_today
    title: "Sky snapshot for a place and moment"
    backing_endpoint: /v2/today
    source_operation: openapi/cyclecalcs-astronomy-openapi-original.json#getToday
    input_schema: present   # live tools/list returns a full JSON Schema per tool
    output_schema: present
  - name: astro_sun
    title: "Sunrise, sunset and twilight"
    backing_endpoint: /v2/sun
    source_operation: openapi/cyclecalcs-astronomy-openapi-original.json#getSun
    input_schema: present   # live tools/list returns a full JSON Schema per tool
    output_schema: present
  - name: astro_moon
    title: "Moon state and appearance"
    backing_endpoint: /v2/moon
    source_operation: openapi/cyclecalcs-astronomy-openapi-original.json#getMoon
    input_schema: present   # live tools/list returns a full JSON Schema per tool
    output_schema: present
  - name: astro_moon_phases
    title: "Lunar phase calendar"
    backing_endpoint: /v2/phases
    source_operation: openapi/cyclecalcs-astronomy-openapi-original.json#getPhases
    input_schema: present   # live tools/list returns a full JSON Schema per tool
    output_schema: present
  - name: astro_positions
    title: "Precise positions of bodies"
    backing_endpoint: /v2/positions
    source_operation: openapi/cyclecalcs-astronomy-openapi-original.json#getPositions
    input_schema: present   # live tools/list returns a full JSON Schema per tool
    output_schema: present
  - name: astro_rise_set
    title: "Rise, transit and set times"
    backing_endpoint: /v2/rise-set
    source_operation: openapi/cyclecalcs-astronomy-openapi-original.json#getRiseSet
    input_schema: present   # live tools/list returns a full JSON Schema per tool
    output_schema: present
  - name: astro_eclipses
    title: "Solar and lunar eclipses"
    backing_endpoint: /v2/eclipses
    source_operation: openapi/cyclecalcs-astronomy-openapi-original.json#getEclipses
    input_schema: present   # live tools/list returns a full JSON Schema per tool
    output_schema: present
  - name: astro_dark_window
    title: "Dark moonless observing window"
    backing_endpoint: /v2/dark-window
    source_operation: openapi/cyclecalcs-astronomy-openapi-original.json#getDarkWindow
    input_schema: present   # live tools/list returns a full JSON Schema per tool
    output_schema: present
  - name: astro_planet_board
    title: "All planets at a glance"
    backing_endpoint: /v2/planet-board
    source_operation: openapi/cyclecalcs-astronomy-openapi-original.json#getPlanetBoard
    input_schema: present   # live tools/list returns a full JSON Schema per tool
    output_schema: present
  - name: astro_planet_events
    title: "Mercury and Venus apparition events"
    backing_endpoint: /v2/planet-events
    source_operation: openapi/cyclecalcs-astronomy-openapi-original.json#getPlanetEvents
    input_schema: present   # live tools/list returns a full JSON Schema per tool
    output_schema: present
  - name: astro_find_place
    title: "Place name to coordinates and timezone"
    backing_endpoint: /v2/places
    source_operation: openapi/cyclecalcs-astronomy-openapi-original.json#getPlaces
    input_schema: present   # live tools/list returns a full JSON Schema per tool
    output_schema: present
manifest:
  file: cyclecalcs-mcp-tools-list.json
  captured_from: 'POST https://www.cyclecalcs.com/mcp {"jsonrpc":"2.0","id":1,"method":"tools/list"}'
x-evidence:
  fetched: '2026-08-09'
  url: https://www.cyclecalcs.com/mcp
  http_status: 200
  note: >-
    tools/list answered anonymously with all 11 tools including full
    inputSchema and outputSchema. Saved verbatim to
    mcp/cyclecalcs-mcp-tools-list.json.