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

Annotations only cover read-only and non-open-world; the description adds an auth requirement (API key) and a behavioral latency cue that credits land within seconds of payment. It does not describe pagination or rate limits on the polling it recommends, but it clearly exceeds what the annotations provide.

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?

Purpose and auth requirement are front-loaded, and the second sentence delivers the operational guidance efficiently. The parenthetical field list is dense but each field name earns its place as return-value documentation, so nothing is wasted.

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?

With no output schema, the description compensates by enumerating the returned fields, and it supplies the auth prerequisite and the polling-after-payment workflow. An agent has enough to call this correctly and interpret the result.

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 no parameters, so the baseline is 4. The description correctly implies a parameterless call scoped implicitly to the caller's own key.

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 caller's key stamp balance — and enumerates exactly what that balance comprises (plan, monthly stamps used/remaining, prepaid `balance`, free-stamp availability, recent purchases). It also names the sibling `buy_stamps` as the related action, so an agent can place it among the proof/stamp tools without opening a 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?

Gives a concrete trigger: poll after a person pays a `buy_stamps` link, with the latency expectation that credits arrive within seconds. This is clear when-to-use context, though it does not state when not to call it or name any alternative read tools.

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