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

Annotations already cover readOnly, openWorld, idempotent, and non-destructive behavior. The description adds useful facts beyond the annotations: 'no auth required' and the underlying data source (HathiTrust Bibliographic API). It also describes the return content in detail, which is valuable context even with an output schema present.

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 compact and well-structured: it front-loads the action and resource, lists accepted IDs, summarizes return values, routes to a sibling for extended data, and closes with data source and auth status. Every sentence earns its place with no filler or repetition.

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?

With an output schema present, the description doesn't need to detail return fields, but it still does at a useful level. It covers the tool's scope, output, sibling routing, data source, and auth requirement, leaving nothing an agent needs to invoke it correctly.

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 100%, so the baseline is 3. The description adds concrete examples for id_value ('8727632' for oclc, 'pur1.32754075735872' for htid) and explains the meaning of each identifier type in prose, going beyond the schema's enum descriptions.

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 a specific verb ('Look up') on a specific resource (book/serial in the HathiTrust shared digital library) and enumerates the accepted identifier types. It also differentiates from the sibling get_full_record by explicitly directing calls that need authors/publisher/subjects elsewhere, so an agent can distinguish it without opening schemas.

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 names an alternative tool, hathitrust-digital.get_full_record, and states the condition for using it (authors/publisher/subjects). It does not explicitly mention the batch_lookup sibling, but the phrase 'by one identifier' implies a single-lookup scope vs batch, giving clear situational context.

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