Fixed star catalogue

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

Annotations already establish readOnly, idempotent, non-destructive, closed-world behavior, so the bar is lower. The description still adds real value beyond them: the data source (Swiss Ephemeris fixstars.cat), the exact fields returned, the 36-star default flag, and the bright-end trimming behavior.

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?

Two dense sentences front-load what the catalogue contains and its provenance, then close with the optional filter and the key routing fact ('no chart needed'). No filler and no repetition of annotation data.

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?

An output schema exists, so return values need not be spelled out, and the description still sketches the fields. Provenance, the default-set flag, and the static-lookup nature cover everything an agent needs to call it correctly; only the maxMagnitude/schema discrepancy is a blemish.

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?

Zero declared parameters gives a baseline of 4, but the description advertises an optional `?maxMagnitude=` query parameter that does not exist in the input schema (an empty object with no properties). The filtering semantics are explained well, yet the schema/description mismatch could lead an agent to pass a parameter the schema rejects.

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 description names a specific resource — the catalogue of star names the API accepts — and enumerates its fields (traditional name, Bayer designation, constellation, magnitude, 36-star default flag). 'Static lookup, no chart needed' implicitly separates it from the sibling astroway_aspects_fixed_stars, which computes chart-based star contacts, but no sibling is named explicitly.

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?

'Static lookup, no chart needed' and 'The star names this API accepts' give clear context that this is a reference call to resolve valid star identifiers, likely before an aspects call. There are no explicit when-not conditions or named alternatives, so it falls short of a 5.

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