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

Annotations indicate readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false, confirming safe read-only behavior. The description adds behavioral detail by stating the tool returns 'every scanned copy, each flagged full-view or limited based on its rights code,' which is beyond what annotations provide. No contradictions.

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?

The description is two sentences, immediately front-loading the purpose and supported identifiers. Every word adds value (e.g., 'keyless', '18M+ volumes', 'full-view or limited'). No redundancy, ideal length for quick comprehension.

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?

Given the tool's simplicity (two parameters, no output schema), the description adequately covers what it does and what it returns. It mentions rights-based access flags, which is useful. It doesn't need to explain return format since no output schema, but could briefly mention potential result count. Still, fairly complete for a straightforward lookup tool.

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% (both id and id_type have descriptions). The description lists the identifier types (OCLC, LCCN, ISSN, etc.), which matches the schema enum, and adds context about the returned data. However, it doesn't significantly add new meaning beyond the schema; it reinforces what is already present.

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 clearly states the tool's purpose: looking up HathiTrust's digitized-book holdings by a standard identifier. It lists specific identifier types and what is returned (bibliographic records and scanned copies). This tool is distinct from siblings like search_within or get_record, and the description immediately conveys its specific use case.

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 mentions it is 'keyless' and covers 18M+ volumes, which implies ease of use, but it does not explicitly state when to use this tool versus alternatives like search_within or get_record. There is no guidance on when not to use it or which identifier type to prefer for different scenarios.

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