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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds a genuinely behavioral fact not present in annotations: the call is free and requires a receipt_id issued by a prior paid response. It omits whether receipts expire or whether the re-fetched payload is identical, but with annotations carrying safety this is solid.

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?

One sentence, front-loaded with the action and resource, with the clarifying parenthetical placed after the essential information. Every clause earns its place.

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 values need not be described, and annotations cover the safety semantics. The description supplies purpose, parameter provenance and cost behavior; only minor operational details (receipt lifetime, pagination/error behavior on an invalid id) are absent.

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 coverage is 100% and the schema already documents the single parameter including its 'rcpt_...' format. The description's provenance note ('from a paid response') largely restates the schema's own wording, so it adds little beyond the structured field. Baseline 3 applies.

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 ('Re-fetch a previously paid result') plus the selection key ('by receipt id'), and adds the key differentiator that this path is free. No sibling tool overlaps, so an agent can identify this as the free retrieval path for a paid result without opening the 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?

The description tells the agent the precondition (you must hold a receipt_id) and where that id comes from ('every paid response carries receipt_id'), which implies the when-to-use condition: retrieving a result already paid for rather than paying again. It does not explicitly name an alternative or a when-not-to-use case, but the context is clear.

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