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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds useful context ('Free', 'public receipts feed') but does not disclose return format, pagination, or any errors or limitations. This is acceptable given the annotation coverage, but the description itself remains thin.

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 description is extremely short and front-loaded with the 'Free.' qualifier. Every phrase adds information about resource, cost, or source. The structure loses points for the awkward fragment after 'Free.' and for not forming a complete sentence that clearly states the action.

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 read-only tool with a single parameter and strong annotations, the description is minimally adequate: an agent knows it can fetch a receipt by id from a public feed. But it lacks any explanation of what a 'paid-call receipt' is, what output to expect, or whether any additional context such as currency or network is relevant.

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 description coverage is 0%, so the description must compensate. It does indicate that the tool operates 'by id', which maps to receipt_id, and clarifies the id refers to a paid-call receipt. However, it does not explain the parameter name, format expectations, or anything beyond the schema's min/max length constraints.

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 title states a clear verb and resource ('Look up a receipt') and the description narrows it to 'a paid-call receipt by id from the rail's public receipts feed.' This distinguishes the tool from its siblings (e.g., genesis402_call, genesis402_prove), though the sentence fragment 'A paid-call receipt by id' is grammatically awkward and lacks an explicit main verb.

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 little guidance on when to choose this tool over alternatives. It notes the receipt comes from a 'public receipts feed' and is free, but it does not state explicit conditions, exclusions, or mention any sibling tool that might be considered instead.

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