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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so the safety profile is covered. The description still adds non-obvious behavior: unknown slugs produce an error rather than an empty result, and there is a free tier of 100 calls/day without a key — genuine rate-limit disclosure that the schema does not carry.

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?

Two sentences, front-loaded with what is returned, followed by a concrete example, the error case, and cost. No filler; every clause carries information the agent can act on.

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 and a fully documented single parameter, the description needs only to cover errors and limits, which it does. The remaining gap is not pointing at list_categories as the way to obtain a valid slug before calling.

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% with a single documented 'slug' property including example values, so the schema does the heavy lifting. The description's example mapping adds only marginal meaning beyond it, which is the baseline-3 case.

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?

States a specific verb and resource ('Returns one category') and enumerates the payload (count, median annualized revenue overall and by tier, ranked members), which sets it apart from list_categories and the business-level get_business tool. The 'one category' framing makes the singular-vs-list distinction obvious.

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 worked example ({"slug":"customer-support"} -> the customer-support agents) plus the 'Unknown slug -> isError' note gives clear invocation context. It stops short of explicit routing guidance, e.g. that list_categories should be used to discover valid slugs before calling this.

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