CycleCalcs Astronomy

Rise, transit and set times

astro_rise_set

Read-onlyIdempotent

Rise, upper transit, set and lower transit for one body at one location, with an explicit status at extreme latitudes (circumpolar, never rises) instead of missing values. Accepts fixed radec targets. For the Sun specifically, astro_sun returns richer twilight structure; for positions between events use astro_positions.

Input Schema

TableJSON Schema

Name	Required	Description
`tz`	No	IANA timezone like "Europe/Lisbon" to render event times in local time. Optional; a resolved place supplies its own timezone.
`end`	No	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.
`lat`	No	Latitude in decimal degrees, north positive. Send lat and lon together.
`lon`	No	Longitude in decimal degrees, east positive (Lisbon is about -9.14). Send lat and lon together.
`body`	Yes	One of sun, moon, mercury, venus, mars, jupiter, saturn, uranus, neptune, pluto, or a fixed J2000 target as "radec:RA,DEC" with RA in hours (0-24) and DEC in degrees (-90..90), e.g. "radec:5.6,-5.4" for the Orion Nebula region.
`date`	No	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.
`place`	No	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.
`start`	No	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.
`cursor`	No	Opaque pagination cursor from a previous result's next_cursor. Send it with the same start/end arguments as the first page.
`search_horizon_days`	No	How many days ahead to search when an event does not occur on the requested day (high latitudes).

Output Schema

TableJSON Schema

Name	Required	Description
`data`	Yes	Rise, transit and set for one body, for a day or across a range.
`rights`	No	Either unrestricted, or attribution_required when third-party place data was used. When attribution_required, the attribution line must be shown.
`warnings`	No	Machine-readable notices about this answer. Present only when non-empty. Never changes whether the call succeeded.
`attribution`	No	The credit line to display verbatim when rights is attribution_required.
`next_cursor`	No	Present only when more rows exist. Send it back with the SAME start/end arguments as the first call to get the next page.
`not_computed`	No	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".

Schema Changelog

Changes observed during successful MCP inspections.

Changed3 schema fields changedSep 27, 2026

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."

Changed1 schema field changedAug 9, 2026

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": "Rise, transit and set for one body, for a day or across a range.",
+      "properties": {
+        "body": {
+          "description": "SINGLE MODE: the events, with a status covering the polar cases where a body never rises or never sets.",
+          "type": "object"
+        },
+        "days": {
+          "description": "RANGE MODE ONLY: one entry per day.",
+          "type": "array"
+        },
+        "window": {
+          "description": "The day 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"
+}

First observedAug 9, 2026

TDQS

A4.2/5.0

Behavior4/5

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

Annotations already establish read-only, idempotent, non-destructive, closed-world behavior, so the safety profile is covered. The description earns credit for a genuine behavioral disclosure beyond structured data: extreme-latitude results return explicit statuses instead of missing values, which tells the agent how to interpret output. It does not cover pagination or any rate/limit behavior.

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, front-loaded with the primary operation and the extreme-latitude output nuance, followed by sibling routing. No filler or restated title/name.

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

Completeness4/5

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

An output schema exists, so return values need no explanation, and the description covers scope, edge-case behavior and alternatives. It is slightly incomplete in not signaling that the tool supports a daily-series mode (start/end) or pagination via cursor, which an agent would only discover from the schema.

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

Parameters3/5

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

Schema description coverage is 100%, with each parameter documented in-schema including radec syntax, IANA tz, date formats and the DATE_OUT_OF_RANGE boundary. The description only echoes the radec-target acceptance, adding little beyond the schema, so baseline 3 applies.

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 a specific computation ('rise, upper transit, set and lower transit for one body at one location') and even discloses the edge-case output contract (explicit circumpolar/never-rises status rather than missing values). It also explicitly distinguishes itself from astro_sun and astro_positions, so an agent can route without opening the 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?

Names two alternatives with selecting conditions: astro_sun for richer twilight structure on the Sun, astro_positions for positions between events. That is clear sibling routing, but it omits guidance on the multi-day series mode (start/end) and cursor pagination that the tool also supports, so it is not fully exhaustive.

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

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