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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered; the description adds the non-obvious economics — the call is FREE, part of the payload requires a key, and a key unlocks balance and day budget. This auth/cost tiering is exactly the kind of context annotations cannot express. It does not say whether results are cached or localized beyond the language parameter.

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?

One dense sentence that front-loads "FREE" and the payoff, with zero filler. The parenthetical about the key is slightly compressed but readable, and the call-to-action closes it cleanly.

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 carry the return contents — and it does, listing actions, fields, pricing, limits, and key-gated balance. Combined with the free/key distinction, an agent knows what to expect back; only the response shape (structured vs. prose) is left unspecified.

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?

The single optional parameter has 100% schema coverage including its enum values and a note that it governs the language of `tell_your_user`. The description adds nothing about the language parameter, so the schema does all the work — the baseline 3 for full coverage 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 enumerates exactly what the tool returns — available actions, fillable fields with per-record price, free limits, and (with a key) balance and day budget — which is specific enough to distinguish it from the operational siblings (check_records, enrich_records, find_person). The verb is implicit in the tool name rather than stated, so it falls just short of a 5.

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?

"Call this first if unsure" gives a clear entry-point rule that no sibling offers. It stops short of saying when NOT to call it (e.g. once you already know the action and fields), so there is no explicit exclusion.

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