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

Annotations already declare readOnlyHint=true, but the description adds real value: 'never calls or pays the APIs it describes' clarifies there is no cost or side effect on third-party services, and it describes the return contents (price per call, reliability score, usage, ranked alternatives, links). It could still say more about failure modes when no match is found, so not a 5.

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 routing condition is front-loaded and the return explanation follows logically; every part is relevant. The long enumerated category list is the one slightly bloated section, though it does usefully signal coverage breadth.

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?

There is no output schema, so the description must explain the return value, and it does so concretely (recommended API plus price, reliability, real usage, ranked alternatives and links). Combined with its usage trigger and coverage list, an agent has everything needed to call and interpret this tool.

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 description coverage is 100%, so each of the four parameters (task, recent, hide_flags, max_price_usd) is already documented in the schema itself. The description adds no parameter-level detail beyond what the schema provides, so the baseline 3 applies.

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 gives a specific verb and resource ('find/recommend the best API for a task') and frames the situation precisely: a task needs an outside API and the agent has not yet picked one. That framing implicitly separates it from the check_endpoint/compare_category siblings, and the concrete example tasks make the scope unmistakable.

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 states exactly when to call it ('when a task needs an outside API or data source and you have not picked one') and backs that up with a dozen representative example tasks. It does not explicitly name alternative siblings or when-not to use it, which keeps it short of a 5.

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