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CycleCalcs Astronomy

by com.cyclecalcs

Dark moonless observing window

astro_dark_window
Read-only

The genuinely dark, moonless observing window for a night: astronomical night intersected with the Moon being down, ranked across up to 62 nights with a trend. The right tool for "when should I stargaze / photograph the Milky Way / observe deep-sky objects". Location required. For plain twilight times use astro_sun.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
tzNoIANA timezone like "Europe/Lisbon" to render event times in local time. Optional; a resolved place supplies its own timezone.
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.
dateNoNight to start from. 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.
placeNoPlace 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.
nightsNoHow many nights to evaluate and rank. Default 1.
moon_illumination_maxNoTreat the Moon as tolerable below this illuminated fraction (0..1) even when up.

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
dataYesThe best genuinely dark observing windows across a range of nights.
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".

TDQS

A4.4/5.0
Behavior4/5

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

Annotations already indicate readOnlyHint=true and openWorldHint=false, so the description adds value by describing the computational logic (intersection of astronomical night and Moon down), the ranking across up to 62 nights, and the trend. It also notes the location requirement. This goes beyond the annotation hints without contradicting them.

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?

The description is two short sentences, front-loading the definition and then giving usage guidance. Every clause adds value; the alternative tool is named in a single subordinate clause. No waste.

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?

For a tool with 7 parameters and an output schema, the description covers the core purpose, intended use cases, alternative tool, and a key prerequisite. It doesn't explain the output schema, but that's covered by the existing output schema. The only minor omission is the meaning of 'trend', but that is not essential for tool selection.

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?

The schema covers 100% of parameters with detailed descriptions, giving a baseline of 3. The description adds only the high-level note 'Location required' and does not provide additional parameter-level detail, so the schema remains the primary source.

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?

The description clearly states the tool provides 'the genuinely dark, moonless observing window for a night' by intersecting astronomical night with Moon-down periods, and explicitly names its intended use cases ('stargaze / photograph the Milky Way / observe deep-sky objects'). It also differentiates from sibling astro_sun for plain twilight times.

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

Usage Guidelines5/5

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

It gives an explicit when-to-use: 'The right tool for "when should I stargaze / photograph the Milky Way / observe deep-sky objects".' It also names an alternative: 'For plain twilight times use astro_sun.' The prerequisite 'Location required' is also stated.

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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TDQS

A4.4/5.0
Disambiguation5/5

Each tool targets a distinct observational need: dark windows, eclipses, geocoding, moon state, phase calendar, planet overview, planet events, precise positions, rise/set times, broad snapshot, and solar day. Cross-references among descriptions prevent ambiguity despite overlapping data like rise/set times appearing in several tools.

Naming Consistency4/5

All tools share the astro_ prefix and use snake_case, creating a predictable pattern. The naming is mostly noun-based (the object of interest), but astro_find_place and astro_rise_set break the pure-noun pattern, introducing a slight inconsistency.

Tool Count5/5

With 11 tools, the server covers the major areas of practical astronomy without redundancy. Each tool provides a distinct calculation or data set, and the count fits the expected scope for an astronomy API.

Completeness4/5

The tool set covers solar, lunar, planetary, eclipse, positional, and visibility needs comprehensively. However, there is no explicit tool for equinoxes and solstices, which would be a natural inclusion for a cycle-focused astronomy server, creating a minor gap.

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