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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is covered. The description goes beyond annotations by naming the source catalogue, the return fields, and the cost/free-tier limit, which adds useful context. However, it does not describe pagination, result format, or behavior on no matches, leaving some behavioral gaps.

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 front-loaded: it leads with the core search capability and return fields, then gives the source and pricing in a second sentence. The pricing detail is not strictly necessary for invocation but is still concise and informative. No filler or redundancy.

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 simple read-only search tool with no output schema, the description covers the essential operational context: what can be searched, what data is returned, the catalogue source, and cost. It falls slightly short on explaining the shape or multiplicity of results, but the listed return fields and simple parameter set make the tool reasonably complete for an agent.

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 only 50%, so the description must compensate. It adds 'subject' as a valid query dimension that the schema's query description ('title, author or ISBN') omits, expanding parameter semantics. The 'limit' parameter is not explained in the description, though its role is partially inferable from the schema's default and bounds.

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 opens with a specific verb and resource: 'Find books by title, author, subject or ISBN'. It then enumerates concrete return fields and names the data source (Open Library/Internet Archive), making the tool's identity and scope unmistakable and clearly distinct from sibling search tools like arxiv_search or hn_search.

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?

While it does not explicitly name alternative tools or exclusion criteria, the description makes the intended use case clear: search the Open Library catalogue for book metadata. The '30M+ titles' scope and the list of searchable keys give sufficient context for an agent to know when this tool is appropriate, though it does not explicitly say when not to use it.

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