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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds genuinely new behavioral context the annotations cannot carry: a metered cost model with a free daily allowance and per-call overage pricing. It stops short of describing result limits or pagination.

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 short sentences with zero filler; the core purpose is front-loaded and the cost caveat follows. Every sentence earns its place.

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 one-parameter search tool with an output schema present, the description covers purpose and the notable cost dimension, so an agent can call it correctly. The remaining gap is routing guidance against the many sibling search tools, which is not strictly required to invoke this one.

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?

There is a single parameter 'q' and schema description coverage is 100%, so the schema already documents it. The description adds no syntax or field-targeting detail (e.g., author:, title:, DOI-style queries), leaving parameter semantics entirely to the schema.

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 verb and resource: 'Bibliographic search across Crossref works.' An agent knows this searches the Crossref corpus rather than fetching or listing other entity types. It does not, however, distinguish itself from the sibling crossref__doi (lookup by identifier) or crossref__journal, so the differentiation is left to naming.

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 description only explains billing ('free within the daily allowance, then $0.003 USDC per call'). It gives no guidance on when to search with this tool versus resolving a known DOI via crossref__doi, or versus the PubMed/arXiv/Semantic Scholar search siblings.

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