Ask the payee whether it accepts this payment (free)

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

Adds substantial context beyond the annotations: it is rule-based (not model judgement), readiness derives from the public registry enforcement ladder, the payer address is screened in reverse, and details the response shape (statuses, reason codes, requested_fields only on hold, evidence, signature). It does not explain the non-read-only/non-idempotent side effects implied by readOnlyHint=false and idempotentHint=false, which is the remaining gap.

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 and the settle-time trigger, then progressively adds statuses, behavior, and cost. It is dense with parenthetical URLs and multi-clause sentences, but essentially every sentence carries information, so little is wasted.

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?

With no output schema, the description correctly enumerates the return values and their conditional fields, and states the cost/auth posture (free, no API key). The only omission is the reason behind the non-read-only annotation, but for a query-style decision tool this leaves nothing an agent needs to call it correctly.

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 already 100%, but the description adds meaning: payee is a registry sid (with a reference), payerAddress is reverse-screened, and amount/purpose/KYA requirements are driven by the payee's own policy rather than fixed rules. This contextualizes the parameters beyond their schema prose.

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+resource: asking the registered payee (by registry sid) whether it accepts an incoming payment, and explicitly frames itself as 'the other half of a safe agent payment,' distinguishing it from the payer-side siblings. An agent knows exactly what this does without opening the schema.

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?

Gives a clear trigger ('before settling, ask the registered payee') and a strong retry exclusion ('decline is final — re-paying does not change it'). It stops short of naming a specific alternative tool (e.g. payment_decision) for the complementary side, so the when-vs-what routing is implied rather than explicit.

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