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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), so the description's job is to add context - and it does, disclosing the upstream data source (Datamuse API) and a per-call cost of 1 credit, both of which matter for agent planning and budgeting. It stops short of describing result shape (whether words come back ranked/scored) or how the two parameters interact.

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?

Three short sentences with the core action front-loaded, followed by usage context, provenance, and cost. No filler, no restatement of the tool name, and the cost note is compactly placed at the end where it does not obstruct the primary definition.

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 simple, read-only, two-parameter lookup with full schema coverage and no output schema, the description covers purpose, domain (English words), provenance, and cost adequately. The only real omission is any hint about what comes back - a bare word list versus ranked/scored matches - which would help an agent decide how to consume results.

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 description coverage is 100%, so the baseline is 3 and the description adds no parameter meaning at all - neither 'word' nor 'limit' is mentioned. Worth noting the schema itself is internally inconsistent (limit is typed as string while described as an integer 1-100, and no parameter is actually marked required despite 'word' being labelled required), and the description does nothing to compensate for that confusion.

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 opens with a specific verb and resource: 'Finds words that rhyme with a specific English word,' which is unambiguous and immediately actionable. It does not, however, differentiate itself from close siblings in the listing such as words_sounding_like, synonyms_for_word, or words_meaning_like, so an agent must infer the boundary itself.

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?

The sentence 'Useful for creative writing, poetry, and lyrics' implies a use context but never states when to choose this tool over its near-neighbours (e.g., words_sounding_like for near/slant rhymes, synonyms_for_word for meaning). There are no exclusions or alternatives, so routing depends on the agent's own reading of sibling names.

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