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

Annotations already declare readOnlyHint and openWorldHint, and the description adds real context beyond them: returns JSON records, defaults to 25 items, ceiling of 500, and a per-record billing model charged against free allowance then credit. However, it never says where maxItems is supplied (it is not a top-level schema property, so it presumably lives inside params), and it omits error/failure behavior and whether partial results are possible.

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 dense sentences, front-loaded with the action and its prerequisite, followed by output shape, paging limits, and cost. Every clause carries information the agent needs; nothing is padding.

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 generic API-proxy tool with only two parameters and no output schema, the description covers prerequisite, return type, result volume, and cost. It leaves out failure modes and the exact location of maxItems, which are the only meaningful gaps.

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 the baseline is 3; the description earns above baseline by telling the agent that `params` values should be derived from describe_api rather than guessed. It also mentions maxItems, which adds meaning but muddies semantics since that field is absent from the declared schema properties.

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 ('Run one API'), and scopes it to a single API using parameters obtained from describe_api, which distinguishes it from search_apis and describe_api. The 'one' vs the sibling discovery tools makes the distinction inferable but never names an alternative explicitly.

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?

Implies—fairly clearly—a two-step workflow: call describe_api first, then pass its parameters here. It does not state exclusions (e.g., when to use search_apis instead, or what happens if the api id is unknown), so guidance is clear context without explicit when-not rules.

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