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

With empty annotations, description must disclose behavior. Only states data source and input, omits rate limits, data freshness, error handling, or what happens with invalid ISBNs.

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?

Extremely concise (5 words) and front-loaded, but lacks useful information. Every word earns its place, but content is insufficient.

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?

Tool is simple with one parameter and no output schema, but description fails to explain return structure or error behavior. Incomplete for agent to use confidently.

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 0%, and description adds no meaning beyond parameter name 'isbn'. Does not specify expected format (e.g., 10/13 digits, hyphens).

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?

Description clearly states it retrieves book metadata by ISBN using Open Library. Verb 'lookup' and resource 'book' are specific, and no sibling tool has similar function.

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?

No guidance on when to use this tool versus alternatives or conditions for use. No mention of limitations or prerequisites.

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