Check whether a request was paid

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

Annotations already declare readOnly/idempotent/non-destructive, and the description reinforces this without merely repeating it ('reports what the chain says and changes nothing, here or in the app'). The genuinely valuable addition is the disclosure that it scans only the newest 200 transactions, which tells the agent a negative result is not proof of non-payment. It stops short of describing the response shape, which matters since no output schema exists.

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?

Three tight sentences, front-loaded with the matching mechanism, followed by the safety profile and the scan limit. Every sentence carries distinct information with no repetition of the title or annotations.

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 two-parameter read-only lookup with full annotation coverage, the description covers mechanism, safety, and the main accuracy caveat. The notable gap is the return value: with no output schema, an agent cannot tell whether it gets a boolean, a matching transaction, or a confirmation count.

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%, so the baseline is 3; the description earns a bump because it explains how the id parameter is actually used — transformed into the nimbooks:invoice:<id> reference tag that the search keys on — which the schema alone does not convey. The address parameter's default behavior is left entirely to the schema.

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 ('looks for a payment tagged with a request's reference') and names the exact tag format (nimbooks:invoice:<id>), so the agent knows precisely what matching logic runs. It also implicitly distinguishes itself from create_payment_request by consuming that tool's id, and from generic listing tools like list_transactions by being a targeted 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?

It gives clear context for when this is the right call (verifying whether a payment request has been settled, using the app's own matching rule) but never states exclusions or names the alternative to use when the payment is older than the scanned window — e.g. falling back to list_transactions or get_statement.

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