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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description adds genuinely useful context the annotations lack: the response is byte-for-byte what a paid call returns, making it a faithful preview rather than a truncated teaser. It does not mention any rate limit, quota, or whether repeated samples are capped, which is the main remaining gap.

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, zero waste, and the payoff ('so you can check the fields, dates and coverage before you pay') is front-loaded alongside the core action. The parameter guidance follows naturally in the second sentence.

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 only one required enum parameter, no output schema, and annotations covering safety, the description is complete: it explains the value proposition, the fidelity of the return, and where to obtain valid endpoint keys. Nothing an agent needs to call it correctly is missing.

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% and the enum already lists all 14 valid keys, with the schema description itself pointing at list_endpoints. The description restates the same guidance plus a few example keys, adding no syntax or format detail beyond the structured field, 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?

States a specific verb+resource (get a free sample answer from a paid endpoint) and clarifies the scope: one endpoint, returned exactly as a paid call would return it. This is clearly distinguishable from list_endpoints (which enumerates keys) and get_free_series (which is a specific series), so an agent can route without opening a 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?

Gives clear when-to-use context ('check the fields, dates and coverage before you pay') and routes the agent to list_endpoints as the source of valid endpoint keys. It does not explicitly state when not to use it (e.g., after subscribing, or for bulk pulls), so it stops short of a full alternative/exclusion statement.

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