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

With no annotations, the description carries the full burden. It discloses the key behavioral fact that authentication via API key is required and characterizes the data as a public read set, but says nothing about rate limits, error behavior, or whether the call has side effects. Adequate but incomplete for a tool with zero annotation coverage.

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 with zero filler. The data-scope statement is front-loaded and the auth requirement follows immediately; nothing could be trimmed without losing information.

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 summarize returns, which it does by naming the data set (credit balance and plan). For a one-parameter, read-only quota tool this is nearly complete, with only return-format or pagination detail 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 description coverage is 100% and the single api_key parameter is fully documented in the schema, including that it is optional if already supplied via the x-api-key header. The description only restates the auth requirement, adding no syntax or format detail beyond the schema.

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: returns credit balance and plan data. It is clearly distinct from the sibling CPF lookup tools, though it does not explicitly name them to reinforce the distinction. A precise endpoint equivalence (GET /quota) anchors the purpose.

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 implies the use case (checking balance/plan) but never states when to call it versus the lookup_cpf siblings, nor any preconditions beyond auth. The endpoint equivalence gives indirect context but no explicit when/when-not guidance.

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