Get the key's plan and quota usage

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

The annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the description's lower requirement is met. The description still adds behavior beyond the structured fields: it explains how billing works ('Paid plans count returned records per month, the demo counts data requests') and confirms the call is free and spends no quota. It also warns that the returned `data` is untrusted listing text and must not be treated as instructions, which is a safety trait absent from the annotations.

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 description is only two short sentences and is front-loaded with what the tool returns and when to use it. The final sentence about untrusted `data` carries a distinct safety payload, so it earns its place rather than padding the text.

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?

An output schema exists, so return-value documentation can live there, and the description does not need to repeat it. For a zero-parameter, read-only quota check, the description covers purpose, billing model, and safe handling of the response, so it is complete enough to call correctly.

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?

With zero parameters, the baseline expectation is 4, and nothing in the description is needed to clarify inputs. The description does not invent input semantics, so it adds no unsupported claims.

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 uses a specific noun phrase: 'The API key's plan, term, quota limit and how much of it is spent, in total and per market.' This states exactly what resource is returned, and none of the sibling tools (search_cars, get_car, get_changes, list_brands, list_models, get_dictionaries, get_markets) covers quota, so the tool is easy to distinguish.

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 description gives clear usage triggers: 'Use it before a large search, or for "how much quota is left".' That tells the agent both when it is useful and what user question it answers. However, it does not name alternatives or state when not to call it, which keeps it below a 5.

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