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 genuinely useful context the annotations do not carry: 'Não consome requisições' tells the agent the call is free against the quota, which materially affects call strategy. It does not describe the shape or granularity of the returned plan/usage data.

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?

Three short sentences with no filler, and the useful part (what it returns, that it costs nothing, that it is a good first test) is front-loaded. Nothing is repeated from the title or schema.

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 zero-parameter, read-only introspection tool with no output schema, the description covers what comes back (plan plus daily and minute usage) and why to call it. Only the overlap with the 'consumo_do_plano' sibling remains unaddressed.

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 tool takes zero parameters, so the schema imposes nothing to explain and the baseline is 4. The description correctly implies no input is required by framing the tool as a pure introspection call.

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: it shows the key's plan and how much of the daily and minute quota is already consumed. It is clear on its own, but it never distinguishes itself from the sibling tool 'consumo_do_plano', which sounds like it covers overlapping ground, so an agent cannot fully disambiguate from the text alone.

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 an explicit usage context: 'Bom primeiro teste para confirmar que a chave funciona' tells the agent to use it as an initial key-validation call. It stops short of naming when to prefer 'consumo_do_plano' instead, so the routing between the two quota-related siblings is left to inference.

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