Look up a receipt (free)

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

Annotations declare readOnlyHint=true and openWorldHint=true, and the description adds valuable context: it is free/no-payment, returns JSON, and returns an error with HTTP status if the id is not found. This goes beyond the annotations, though it doesn't cover rate limits or authentication, which are minor for a free read-only tool.

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?

Two sentences with no filler. The 'Free, no payment' note is front-loaded, and the main action and outcome are stated efficiently. 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 single-parameter lookup with full schema coverage and no output schema, the description explains the return format (JSON) and error behavior (HTTP status), making it sufficient for an agent to call correctly. Minor details like rate limits are not necessary 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?

Schema coverage is 100% with the parameter described as 'The receipt id returned with a paid call result.' The description reiterates the receipt-id nature and mentions error on not-found, but adds little beyond what the schema already conveys.

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 ('Fetches'), a resource ('one paid-call receipt by id'), and a purpose ('to confirm a call was paid and delivered'). It clearly distinguishes from siblings like genesis402_call (which likely initiates calls) by focusing on receipt lookup.

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?

Provides clear context for when to use: 'to confirm a call was paid and delivered' indicates the intended use case. However, it does not explicitly mention exclusions or alternative tools among the sibling list, so it stops short of a 5.

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