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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, and the description reinforces rather than contradicts them. It adds real context beyond the annotations: data reflects 'only what Suara has on record' rather than a live billing lookup, and that billing modifications are out of scope. The phrase 'Read only' is redundant with readOnlyHint, and the response shape is not described, keeping this below a 5.

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?

Front-loaded with an explicit 'Use this when...' trigger, followed by a compact enumeration of returned facts. Two clauses ('Read only' and 'Billing changes aren't made here') largely restate each other and the annotations, but the waste is minimal.

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 with no output schema, the description does the necessary work by specifying which four facts come back, so an agent knows what to expect. Only the behavior when no plan exists on record is left implicit, which is a minor gap.

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 there is nothing for the description to disambiguate; the baseline for a no-param tool applies. The description correctly implies the subject is scoped to the signed-in owner, which is the only semantic clarification needed.

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 resource (the signed-in owner's Suara plan/billing) and enumerates exactly what it reports: payment status, start date, weekly inclusions, and remaining allowance. No sibling tool covers billing, and the description makes the scope unmistakable without opening any 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?

Names a clear trigger ('when the signed-in owner asks about their Suara plan or billing') and an explicit exclusion ('Billing changes aren't made here'), which steers the agent away from expecting mutation. It does not name an alternative tool for billing changes, though no sibling appears to serve that need, so the gap is small.

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