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

The description adds substantial context beyond the readOnly and openWorld annotations: it requires CAT_API_KEY, returns 503 without it, costs $0.002 per successful call via x402, and failed calls are not charged. These are exactly the operational details an agent needs before invoking the tool.

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 front-loaded with the resource and returned fields, then moves to filtering and operational constraints. It is information-dense, though the meta note about being in the batch's wish list is slightly less essential than the surrounding technical details.

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 that an output schema exists, the description need not explain return values. It covers the data fields, filtering, API key requirement, failure behavior, and pricing, leaving no major operational gap for invoking the tool 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 both parameters are already documented in the input schema. The description adds useful example filter terms for q, but does not add information about the limit parameter; this matches the baseline 3 when the schema does the heavy lifting.

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 identifies a specific resource (cat breeds from TheCatAPI), enumerates the returned fields, and explicitly distinguishes itself from the surrounding job tools by stating 'Not a job data source'. An agent can tell exactly what this tool retrieves without opening the schema.

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?

It explains the optional filtering behavior with concrete examples ('turkish', 'Egypt') and clarifies that the tool is not job-related. It does not frame explicit when-to-use/when-not-use alternatives beyond the non-job disclaimer, but the context is clear enough.

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