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

Annotations already declare readOnlyHint=true, destructiveHint=false, idempotentHint=true, openWorldHint=true, so the safety profile is clear. The description adds no extra behavioral traits beyond listing the data fields. It does not disclose rate limits or data freshness, but annotations cover the essential safety aspects.

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 a single, front-loaded sentence that conveys all key information: input method, output fields, and data source. No unnecessary words. It is efficiently structured.

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 low complexity (one parameter, clear purpose) and the presence of an output schema, the description is complete. It covers the input, output, and source adequately. No gaps remain.

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?

The input schema has one required parameter 'isbn' with a description that includes examples. Schema description coverage is 100%. The description adds clarification that accepts ISBN-10 or ISBN-13, but this is already implied by the schema. The parameter semantics are adequately covered by the schema, so the description adds minimal extra value.

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: 'Look up a book by ISBN-10 or ISBN-13' and lists the returned data (title, author, publisher, pages, cover image, subjects). It also mentions the source and scale (40M+ books from Open Library/Internet Archive). This distinguishes it from sibling tools that search by other criteria.

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 implicitly tells the agent to use this tool when an ISBN is available. It does not explicitly state when not to use it or mention alternatives, but the specificity makes the usage context clear. No misleading guidance.

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