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

Annotations only declare readOnlyHint and openWorldHint; the description goes further by disclosing cost behavior (no points spent) and a specific failure mode: supplying fields yields privacy_consent_required until the controller accepts the current privacy version, with an explicit warning not to fabricate acceptance. That is real behavioral context an agent could not infer from the annotations or schema.

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?

Four short sentences, front-loaded with the purpose before the constraints. The privacy-consent warning earns its place as an operational guard, and there is no filler, though the 'Do not invent that acceptance' line slightly restates the preceding sentence.

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 read-only lookup with no output schema, the description covers returns (title, first author, DOI), cost, and one error path. It omits query format and what happens when Crossref returns multiple candidate works — an ambiguity an agent will hit immediately and cannot resolve from any structured field.

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% for the single required 'query' parameter, so the description must carry the burden, yet it never says what to put in 'query' — a title string, a citation, a DOI, or free text. The phrase 'does not accept a URL' is the only hint about acceptable input, and the 60-character limit is left 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 (look up) and resource (one scholarly work in Crossref) and even names the returned fields: title, first author, DOI. It is clearly a bibliographic metadata lookup, which separates it in spirit from hub_arxiv, though it never names a sibling 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?

Gives useful negative guidance: 'This is metadata, not the full text', 'does not spend points', 'does not accept a URL'. That rules out several wrong invocations, but it never points to the alternative tool (e.g. hub_arxiv) or states when a caller should prefer one over the other.

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