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CycleCalcs Astronomy

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Moon state and appearance

astro_moon
Read-onlyIdempotent

The Moon at an instant or as a daily series: phase name and angle, illuminated fraction, distance, apparent size, libration, bright limb, and the next quarter phases. A location adds rise/set and altitude. For a calendar of new and full moons use astro_moon_phases; for the Moon's exact coordinates use astro_positions.

Input Schema

NameRequiredDescriptionDefault
tzNoIANA timezone like "Europe/Lisbon" to render event times in local time. Optional; a resolved place supplies its own timezone.
endNoLast day of a daily series. ISO 8601 UTC date or datetime, e.g. "2026-08-06" or "2026-08-06T21:00:00Z". With a location, a bare date means that date there: its day, its evening and its night. Or jd: followed by a Julian Day on the UT scale, e.g. "jd:2461000.5". On astro_positions, date may list up to 24 datetimes separated by commas, answered in the order sent. Omit for the current moment. Years 1700 to 2200 only; outside that range the API refuses with DATE_OUT_OF_RANGE because the ephemeris is not reliable there.
latNoLatitude in decimal degrees, north positive. Send lat and lon together.
lonNoLongitude in decimal degrees, east positive (Lisbon is about -9.14). Send lat and lon together.
dateNoISO 8601 UTC date or datetime, e.g. "2026-08-06" or "2026-08-06T21:00:00Z". With a location, a bare date means that date there: its day, its evening and its night. Or jd: followed by a Julian Day on the UT scale, e.g. "jd:2461000.5". On astro_positions, date may list up to 24 datetimes separated by commas, answered in the order sent. Omit for the current moment. Years 1700 to 2200 only; outside that range the API refuses with DATE_OUT_OF_RANGE because the ephemeris is not reliable there.
countNoNumber of daily rows from start (alternative to end).
placeNoThe place NAME only, one to three words, instead of lat/lon: "City" or "City,CC" with an ISO country code, e.g. "Lisbon,PT". Never a question or a sentence. Resolved server-side; the response then carries a required GeoNames CC BY 4.0 credit in its attribution field, which must be preserved when shown.
startNoFirst day of a daily series. ISO 8601 UTC date or datetime, e.g. "2026-08-06" or "2026-08-06T21:00:00Z". With a location, a bare date means that date there: its day, its evening and its night. Or jd: followed by a Julian Day on the UT scale, e.g. "jd:2461000.5". On astro_positions, date may list up to 24 datetimes separated by commas, answered in the order sent. Omit for the current moment. Years 1700 to 2200 only; outside that range the API refuses with DATE_OUT_OF_RANGE because the ephemeris is not reliable there.
cursorNoOpaque pagination cursor from a previous result's next_cursor. Send it with the same start/end arguments as the first page.

Output Schema

NameRequiredDescriptionDefault
dataYesThe Moon's state and appearance, or a sampled series in range mode.
rightsNoEither unrestricted, or attribution_required when third-party place data was used. When attribution_required, the attribution line must be shown.
warningsNoMachine-readable notices about this answer. Present only when non-empty. Never changes whether the call succeeded.
attributionNoThe credit line to display verbatim when rights is attribution_required.
next_cursorNoPresent only when more rows exist. Send it back with the SAME start/end arguments as the first call to get the next page.
not_computedNoData this API deliberately does not serve, and why. Present only when the question touched such a field. An absence named here is information: treat it as "withheld", never as "none exists".

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changed
    • changedInput schema / properties / place / description
      Previous value: -"Place name instead of lat/lon, as \"City\" or \"City,CC\" with an ISO country code, e.g. \"Lisbon,PT\". Resolved server-side; the response then carries a required GeoNames CC BY 4.0 credit in its attribution field, which must be preserved when shown."New value: +"The place NAME only, one to three words, instead of lat/lon: \"City\" or \"City,CC\" with an ISO country code, e.g. \"Lisbon,PT\". Never a question or a sentence. Resolved server-side; the response then carries a required GeoNames CC BY 4.0 credit in its attribution field, which must be preserved when shown."
  2. Changed3 schema fields changed
    • changedInput schema / properties / date / description
      Previous value: -"ISO 8601 UTC date or datetime, e.g. \"2026-08-06\" or \"2026-08-06T21:00:00Z\". Or jd: followed by a Julian Day on the UT scale, e.g. \"jd:2461000.5\". On astro_positions, date may list up to 24 datetimes separated by commas, answered in the order sent. Omit for the current moment. Years 1700 to 2200 only; outside that range the API refuses with DATE_OUT_OF_RANGE because the ephemeris is not reliable there."New value: +"ISO 8601 UTC date or datetime, e.g. \"2026-08-06\" or \"2026-08-06T21:00:00Z\". With a location, a bare date means that date there: its day, its evening and its night. Or jd: followed by a Julian Day on the UT scale, e.g. \"jd:2461000.5\". On astro_positions, date may list up to 24 datetimes separated by commas, answered in the order sent. Omit for the current moment. Years 1700 to 2200 only; outside that range the API refuses with DATE_OUT_OF_RANGE because the ephemeris is not reliable there."
    • changedInput schema / properties / end / description
      Previous value: -"Last day of a daily series. ISO 8601 UTC date or datetime, e.g. \"2026-08-06\" or \"2026-08-06T21:00:00Z\". Or jd: followed by a Julian Day on the UT scale, e.g. \"jd:2461000.5\". On astro_positions, date may list up to 24 datetimes separated by commas, answered in the order sent. Omit for the current moment. Years 1700 to 2200 only; outside that range the API refuses with DATE_OUT_OF_RANGE because the ephemeris is not reliable there."New value: +"Last day of a daily series. ISO 8601 UTC date or datetime, e.g. \"2026-08-06\" or \"2026-08-06T21:00:00Z\". With a location, a bare date means that date there: its day, its evening and its night. Or jd: followed by a Julian Day on the UT scale, e.g. \"jd:2461000.5\". On astro_positions, date may list up to 24 datetimes separated by commas, answered in the order sent. Omit for the current moment. Years 1700 to 2200 only; outside that range the API refuses with DATE_OUT_OF_RANGE because the ephemeris is not reliable there."
    • changedInput schema / properties / start / description
      Previous value: -"First day of a daily series. ISO 8601 UTC date or datetime, e.g. \"2026-08-06\" or \"2026-08-06T21:00:00Z\". Or jd: followed by a Julian Day on the UT scale, e.g. \"jd:2461000.5\". On astro_positions, date may list up to 24 datetimes separated by commas, answered in the order sent. Omit for the current moment. Years 1700 to 2200 only; outside that range the API refuses with DATE_OUT_OF_RANGE because the ephemeris is not reliable there."New value: +"First day of a daily series. ISO 8601 UTC date or datetime, e.g. \"2026-08-06\" or \"2026-08-06T21:00:00Z\". With a location, a bare date means that date there: its day, its evening and its night. Or jd: followed by a Julian Day on the UT scale, e.g. \"jd:2461000.5\". On astro_positions, date may list up to 24 datetimes separated by commas, answered in the order sent. Omit for the current moment. Years 1700 to 2200 only; outside that range the API refuses with DATE_OUT_OF_RANGE because the ephemeris is not reliable there."
  3. Changed3 schema fields changed
    • changedInput schema / properties / date / description
      Previous value: -"ISO 8601 UTC date or datetime, e.g. \"2026-08-06\" or \"2026-08-06T21:00:00Z\". Omit for the current moment. Years 1700 to 2200 only; outside that range the API refuses with DATE_OUT_OF_RANGE because the ephemeris is not reliable there."New value: +"ISO 8601 UTC date or datetime, e.g. \"2026-08-06\" or \"2026-08-06T21:00:00Z\". Or jd: followed by a Julian Day on the UT scale, e.g. \"jd:2461000.5\". On astro_positions, date may list up to 24 datetimes separated by commas, answered in the order sent. Omit for the current moment. Years 1700 to 2200 only; outside that range the API refuses with DATE_OUT_OF_RANGE because the ephemeris is not reliable there."
    • changedInput schema / properties / end / description
      Previous value: -"Last day of a daily series. ISO 8601 UTC date or datetime, e.g. \"2026-08-06\" or \"2026-08-06T21:00:00Z\". Omit for the current moment. Years 1700 to 2200 only; outside that range the API refuses with DATE_OUT_OF_RANGE because the ephemeris is not reliable there."New value: +"Last day of a daily series. ISO 8601 UTC date or datetime, e.g. \"2026-08-06\" or \"2026-08-06T21:00:00Z\". Or jd: followed by a Julian Day on the UT scale, e.g. \"jd:2461000.5\". On astro_positions, date may list up to 24 datetimes separated by commas, answered in the order sent. Omit for the current moment. Years 1700 to 2200 only; outside that range the API refuses with DATE_OUT_OF_RANGE because the ephemeris is not reliable there."
    • changedInput schema / properties / start / description
      Previous value: -"First day of a daily series. ISO 8601 UTC date or datetime, e.g. \"2026-08-06\" or \"2026-08-06T21:00:00Z\". Omit for the current moment. Years 1700 to 2200 only; outside that range the API refuses with DATE_OUT_OF_RANGE because the ephemeris is not reliable there."New value: +"First day of a daily series. ISO 8601 UTC date or datetime, e.g. \"2026-08-06\" or \"2026-08-06T21:00:00Z\". Or jd: followed by a Julian Day on the UT scale, e.g. \"jd:2461000.5\". On astro_positions, date may list up to 24 datetimes separated by commas, answered in the order sent. Omit for the current moment. Years 1700 to 2200 only; outside that range the API refuses with DATE_OUT_OF_RANGE because the ephemeris is not reliable there."
  4. Changed3 schema fields changed
    • changedOutput schema / properties / data / properties / angular_diameter_arcsec / description
      Previous value: -"Apparent disc size in arcseconds."New value: +"Apparent disk size in arcseconds."
    • changedOutput schema / properties / data / properties / distance_km / description
      Previous value: -"Centre-to-centre distance in kilometres."New value: +"Center-to-center distance in kilometres."
    • changedOutput schema / properties / data / properties / position_geocentric / description
      Previous value: -"Position as seen from Earth's centre."New value: +"Position as seen from Earth's center."
  5. Changed1 schema field changed
    • changedOutput schema / (root)
      Previous value: -nullNew value: +{
+  "additionalProperties": true,
+  "description": "The MCP projection of a CycleCalcs v2 response: the answer, plus the provenance a caller needs to use it honestly.",
+  "properties": {
+    "attribution": {
+      "description": "The credit line to display verbatim when rights is attribution_required.",
+      "type": "string"
+    },
+    "data": {
+      "additionalProperties": true,
+      "description": "The Moon's state and appearance, or a sampled series in range mode.",
+      "properties": {
+        "angular_diameter_arcsec": {
+          "description": "Apparent disc size in arcseconds.",
+          "type": "number"
+        },
+        "bright_limb": {
+          "description": "Which way the lit edge points.",
+          "type": "object"
+        },
+        "constellation": {
+          "description": "The IAU constellation the Moon currently occupies.",
+          "type": "object"
+        },
+        "distance_au": {
+          "description": "The same distance in astronomical units.",
+          "type": "number"
+        },
+        "distance_basis": {
+          "description": "Whether the distance is geocentric or topocentric.",
+          "type": "string"
+        },
+        "distance_km": {
+          "description": "Centre-to-centre distance in kilometres.",
+          "type": "number"
+        },
+        "event_definition": {
+          "description": "The altitude convention rise and set are measured against.",
+          "type": "string"
+        },
+        "fraction_of_mean_distance": {
+          "description": "Distance relative to the mean, for supermoon claims.",
+          "type": "number"
+        },
+        "fraction_of_mean_distance_definition": {
+          "description": "How that fraction is defined.",
+          "type": "string"
+        },
+        "libration": {
+          "description": "The rocking that reveals a little of the far side.",
+          "type": "object"
+        },
+        "magnitude": {
+          "description": "Apparent visual brightness.",
+          "type": "number"
+        },
+        "next_phases": {
+          "description": "Upcoming quarter phases with exact instants.",
+          "type": "array"
+        },
+        "parallax_deg": {
+          "description": "Angular shift between those two viewpoints.",
+          "type": "number"
+        },
+        "phase": {
+          "description": "Phase name, angle and illuminated fraction.",
+          "type": "object"
+        },
+        "position_geocentric": {
+          "description": "Position as seen from Earth's centre.",
+          "type": "object"
+        },
+        "position_topocentric": {
+          "description": "Position as seen from the given location.",
+          "type": "object"
+        },
+        "rise_set": {
+          "description": "Moonrise and moonset for the location.",
+          "type": "object"
+        },
+        "series": {
+          "description": "RANGE MODE ONLY: one sampled entry per step.",
+          "type": "array"
+        },
+        "summary": {
+          "description": "A one-line reading of the Moon right now.",
+          "type": "string"
+        },
+        "tropical_sign": {
+          "description": "Tropical ecliptic longitude, reported as position only.",
+          "type": "object"
+        },
+        "window": {
+          "description": "The instant or range actually evaluated.",
+          "type": "object"
+        }
+      },
+      "type": "object"
+    },
+    "next_cursor": {
+      "description": "Present only when more rows exist. Send it back with the SAME start/end arguments as the first call to get the next page.",
+      "type": "string"
+    },
+    "not_computed": {
+      "description": "Data this API deliberately does not serve, and why. Present only when the question touched such a field. An absence named here is information: treat it as \"withheld\", never as \"none exists\".",
+      "type": "array"
+    },
+    "rights": {
+      "description": "Either unrestricted, or attribution_required when third-party place data was used. When attribution_required, the attribution line must be shown.",
+      "type": "string"
+    },
+    "warnings": {
+      "description": "Machine-readable notices about this answer. Present only when non-empty. Never changes whether the call succeeded.",
+      "type": "array"
+    }
+  },
+  "required": [
+    "data"
+  ],
+  "type": "object"
+}
  6. First observed

TDQS

A4.5/5.0
Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered and the description doesn't need to repeat it. The description still adds real behavioral context: the instant-vs-series duality, and that a location changes the output set (rise/set, altitude). It doesn't mention the pagination flow or error behavior, which are documented in the schema.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Three tight sentences: capability first, location behavior second, sibling disambiguation last. No filler, no restatement of the title, and the most decision-relevant routing information is placed where it will be seen.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With an output schema present, return values need no explanation, and the rich 100%-covered parameter schema handles dates, place, count, and pagination. For a read-only astronomy query tool, nothing an agent needs to call it correctly is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so the baseline would be 3 even with no parameter prose. The description nonetheless adds value by explaining that location parameters unlock additional outputs (rise/set, altitude), which is a semantic link the schema descriptions don't make explicit.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States the specific resource (the Moon) and the two modes it serves (instant or daily series), then enumerates the exact quantities returned: phase name and angle, illuminated fraction, distance, apparent size, libration, bright limb, next quarters. It explicitly distinguishes itself from astro_moon_phases and astro_positions, so an agent can route without opening a schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explicitly names two alternatives and the condition that selects each (calendar of new/full moons → astro_moon_phases; exact coordinates → astro_positions), and notes that supplying a location adds rise/set and altitude. It stops short of routing rise/set requests to the astro_rise_set sibling, which is a small remaining gap.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

All CycleCalcs Astronomy toolsInspect
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