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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the bar is lower. The description still adds real context: the price is the broker's asking price and 'never a sale price', the estimate is only present 'where her page shows one', AIS position carries a timestamp, and every fact is attributed with source and date. That prevents misinterpretation of returned values.

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 sentences, front-loaded with the core purpose, followed by a well-structured enumeration of returned facts and the input forms. Dense but every clause carries information; there is no filler.

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?

Because an output schema exists, return values need not be re-explained, and the description still covers the notable return caveats (asking vs sale price, conditional estimate, timestamped AIS). The only modest gap is the absence of any note on error behavior when no matching yacht is found.

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 100%, so a baseline of 3 is warranted, but the description goes further by explaining the disambiguation purpose of builder and length_m and by stating that the name may be replaced with a yachtfinder.co/y/ link or an id, which the schema only partially conveys.

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?

States a specific resource (one yacht's facts) and enumerates exactly what is returned: builder, year, length, status, asking price, estimate, AIS position, listing location, and the source page. This contrasts implicitly but clearly with the plural siblings find_yachts and yachts_near, so an agent can select it without opening a schema.

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?

Gives concrete instruction on disambiguation: 'add builder or length_m when several yachts share it', and accepts either a name or a yachtfinder.co/y/ link. It names no alternative tool or explicit when-not condition, but the single-yacht scope makes the intended context unambiguous.

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