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

Goes well past the annotations: it discloses finality semantics (only consumed and expired are final; expired reported 5 s after validBefore), the caveat that a settlement already in flight reads as unspent, the auth requirement for certain states, and that it consumes the same per-IP allowance — an explicit rate-limit warning. This is exactly the extra context annotations cannot convey.

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?

Front-loaded with the core purpose, then finality, then auth/rate-limit caveats — a logical order with no filler sentences. It is dense to the point of being slightly packed, but every sentence carries decision-relevant information.

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?

No output schema exists, and the description compensates by explaining every returned state and its finality. Combined with 100% schema coverage and readOnly/openWorld annotations, an agent has everything needed to call it correctly and interpret results.

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, but the description adds genuine semantic meaning: it ties validBefore to the 5 s expiry rule and explains why unspent is provisional rather than final. That elevates it above schema repetition, though the per-parameter formats (nonce hex/decimal) are already in 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 — checks whether a signed payment authorization has been used on chain — and enumerates the concrete return states (unspent, consumed, expired) plus the underlying mechanisms (EIP-3009 authorizationState, Permit2 nonce bitmap). An agent can distinguish it from verify_payment or the config/health siblings purely from this text.

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?

Names the triggering scenario explicitly: 'for a client whose settle reply was lost'. It also clarifies that settled and pending states require the owning API key over HTTP, which tells the agent when this tool is not sufficient. It stops short of naming a sibling alternative (e.g. verify_payment) for the in-flight case, so not a full 5.

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