Almanack

moon_phases

Every moon's phase on a date. 'fraction' is the exact position in the cycle, 0.0 at new and 0.5 at full, and is the number to compute with. 'phase' is only which named bucket that fraction falls in, and 'illumination' is the lit portion of the disc from 0.0 to 1.0. Computed in closed form from the moon's period and offset, not simulated and not astronomical: it is exactly what the spec describes. Measured at the start of the day; pass day_fraction 0.5 for midday, or 'time' to say where in the day exactly for a calendar whose spec divides its day. Give one or the other.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`date`	Yes
`time`	No
`calendar`	Yes
`day_fraction`	No

Schema Changelog

Changes observed during successful MCP inspections. Dates show when Glama detected each change.

Changed1 schema field changedSep 1, 2026

addedInput schema / properties / time

Added value: +{
+  "anyOf": [
+    {
+      "additionalProperties": {
+        "type": "integer"
+      },
+      "type": "object"
+    },
+    {
+      "type": "integer"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "default": null,
+  "title": "Time"
+}

First observedSep 1, 2026

TDQS

A4.3/5.0

Behavior5/5

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

With no annotations provided, the description carries the full behavioral burden, and it delivers: it discloses the closed-form computation model, the non-astronomical nature, the start-of-day measurement assumption, and how to adjust the observation point. This is rich, non-obvious behavioral context beyond the bare 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?

The description is dense but every sentence earns its place: it explains the output semantics, the computation model, the timing convention, and the input choice in a compact paragraph. Nothing is filler, and the most important phrase appears first.

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

Completeness3/5

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

For a tool with no output schema, the description does a good job defining returned values, and it covers the tricky day_fraction/time behavior. But it leaves meaningful gaps: the structure and semantics of the required 'calendar' and 'date' nested objects are not explained, and it does not specify what happens if both day_fraction and time are supplied despite 'Give one or the other.'

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 coverage is 0%, so the description must compensate. It explains day_fraction and time well, including default behavior and mutual exclusivity, and it defines the meaning of the returned fields. However, it gives almost no guidance on the required 'date' and 'calendar' object parameters, which are nested and opaque in the schema.

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 opening line, 'Every moon's phase on a date,' states a specific computation and resource, and the rest of the description defines the output fields (fraction, phase, illumination) in enough detail to distinguish it from the sun/calendar siblings. It is a clear, non-tautological statement of what the tool does.

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?

The description gives explicit conditional guidance on when to pass 'day_fraction 0.5' versus 'time', and instructs 'Give one or the other.' It also draws a boundary around the model ('not simulated and not astronomical'), which prevents misuse. However, it does not explicitly name sibling tools such as sun_daylight or state when to choose them instead.

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

A4.2/5.0

Disambiguation5/5

Each tool targets a distinct date/calendar operation: arithmetic, conversion, weekday lookup, period membership, moon phase, daylight, event queries, formatting/parsing, and two different rendering outputs. Even superficially similar tools (calendar_weekday vs nth_weekday_of_month, calendar_events vs calendar_periods) ask clearly different questions that the descriptions make unambiguous.

Naming Consistency4/5

Names are all lowercase snake_case and mostly follow a verb_first or noun_query pattern, but there is a mix: add_to_date, convert_date, and parse_calendar_date are imperative, while moon_phases, sun_daylight, and calendar_events are noun phrases describing what they return. The calendar_ prefix on three tools and consistent rendering parse/format pairs help readability, so this is a minor deviation, not chaos.

Tool Count5/5

15 tools sits at the upper bound of the ideal range for a focused domain toolkit. Every tool addresses a genuine calendar use case (define, convert, query, render, validate, generate), and none feels redundant or extraneous.

Completeness5/5

The set covers the full lifecycle of working with a custom calendar: validation before use, conversion between representations, date arithmetic and intervals, weekday and period queries, recurring events and daylight/moon data, formatting/parsing, and visual rendering. No obvious dead ends or missing operations come to mind for the stated domain.

Resources

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