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

Annotations only declare readOnlyHint and openWorldHint, yet the description adds substantive behavior: it reads the Atom API, returns titles rather than PDFs, and can return a privacy_consent_required gate that must not be faked. That consent-gating disclosure is exactly the kind of context annotations cannot express.

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, each carrying distinct information (what it searches, what it returns, cost, consent behavior), with no filler. Phrasing is terse to the point of slight fragmentation, but nothing is wasted.

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, no-output-schema lookup, the description covers result shape (titles), cost model, and the consent-block failure mode. The only soft spot is the ambiguous 'if you supply fields' clause, since the sole field is required, leaving the exact trigger condition unclear.

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?

With a single parameter at 0% schema description coverage, the description compensates by characterizing the value as a 'short phrase' and explicitly ruling out a URL, which prevents a common misuse the bare 'string' schema would allow. It does not restate the 1-60 character bounds, but that detail lives in 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 (Search) and resource (arXiv records) plus a scope qualifier (two recent records, short phrase), so the agent knows it hits arXiv rather than a general web index. It never names hub_crossref or hub_wikipedia, so differentiation from scholarly siblings is left to the agent.

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?

Offers constraints rather than routing: 'does not accept a URL' and 'does not spend points' imply usage boundaries, but there is no explicit when-to-use versus the many other hub_* lookup tools. An agent must infer that this is for arXiv specifically.

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