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

Annotations already cover readOnlyHint, idempotentHint, and destructiveHint as false. The description adds that the operation is free and that receipt IDs come from previous paid responses, which provides useful context about the data source and cost side effects beyond the structured annotations. No contradiction with annotations.

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?

The entire description is one concise sentence that immediately states the core action and the key constraint (free, by receipt id), with no redundant phrasing. It is perfectly front-loaded and every word 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?

For a simple retrieval tool with a single parameter and no output schema, the description is sufficient. It explains when the tool is relevant and where the receipt_id comes from. The return value is implied to be the previously paid result, which is clear from the context. Minor gap: it doesn't explicitly state what the response looks like, but this is not essential given the tool's simplicity.

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 schema provides 100% coverage for receipt_id, including its format (rcpt_...). The description only repeats that the receipt id is used, adding no new semantic information beyond what the schema already declares. Baseline 3 is appropriate given high schema coverage.

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?

The description clearly states the action (re-fetch), the resource (a previously paid result), and the mechanism (by receipt id). It explicitly notes the result is free and that every paid response carries a receipt_id, which distinguishes this tool from payment- or generation-focused siblings. The purpose is unambiguous and specific.

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 gives clear context: use this tool when you have a receipt_id from a previously paid response and want to retrieve the result without paying again. It implies the alternative is to re-run the original paid operation, though it doesn't explicitly name a sibling tool. It does not provide exclusions, but the guidance is sufficient for a focused retrieval tool.

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