moon_phase_map

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

With no annotations present, the description carries the burden and does so reasonably well: it declares no auth required, local computation (no external dependency), default location and default month, and states the caller must surface the returned link verbatim because rendering may fail elsewhere. It stops short of describing latency, output size, or what happens with invalid dates.

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

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

The purpose and the caller-facing link instruction are front-loaded, and the Args block is a tight one-line-per-parameter list. The worked query examples are useful but slightly redundant with the opening sentence, which keeps this just short of maximum.

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

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

For a zero-parameter-required tool with no output schema, the description covers scope, defaults, all arguments, and the critical instruction to reproduce the returned link. It leaves the returned payload shape vague (a bare link versus image markup), which is the only gap an agent might stumble on.

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

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

Schema coverage is 0% and the description fully compensates: it documents all six parameters, gives accepted date formats, explains the place/lat/lon precedence rule (lat/lon override place), gives the layout enum values with calendar as default, and bounds days to 3–12 with a default of 8 plus an explicit note that it is ignored in calendar layout.

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

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

The definition names a specific resource and output — a moon-phase map covering one month — and parenthetically states the key operational trait (no authentication, computed locally). It does not explicitly differentiate itself from nearby siblings such as sky_map_with_satellites or solar_system_now, but no sibling plausibly overlaps, so the purpose is unambiguous.

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

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

Three concrete example user utterances show the situations the tool is for, and the defaults (current month, Tokyo) are spelled out so an agent can call it with no arguments. Missing are explicit exclusions or a pointer to an alternative when the user wants a single date's phase rather than a monthly map.

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