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

Annotations only cover readOnlyHint and openWorldHint; the description adds substantial behavior the annotations cannot: an x402 charge model (~$0.01 USDC on Base / XRP / RLUSD on XRP Ledger), a free first call per day, the fact a payment watch is billed from its first call, and that bad input and ledger outages are never charged. Cost and billing-failure semantics are exactly what an agent needs before invoking a paid 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?

Purpose is front-loaded in the first sentence, followed by the use case and then the billing caveats. The pricing paragraph packs four clauses, but each carries decision-relevant information (free first call, price, charging exclusions), 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?

There is no output schema, so the description compensates by enumerating what is verified/returned (validation, result code, destination, destination tag, currency, issuer, delivered amount) plus the cost and error-charging rules. For a 7-parameter paid read tool with 57% schema coverage, nothing essential to calling it correctly is missing.

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 only 57% and two parameters (amount, currency, destination_tag) have no schema description, but the description supplies their meaning: they are expected values the tool checks against the delivered payment, with amount explicitly tied to detecting partial-payment tricks. The network parameter and the required/optional split are still left to the schema, keeping this below a 5.

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?

Specific verb + resource + enumerated verification scope ('validates that an XRP Ledger payment settled as expected: validation, result code, destination, destination tag, currency, issuer, and the amount actually delivered'). It also names the failure mode it defends against (partial-payment tricks), which distinguishes it from siblings like payment_watch or token_check without needing to open a 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 use context: 'Useful when confirming that a customer or counterparty really paid.' It also implies a division of labour with payment_watch via the pricing note ('a payment watch is paid from the first call'), so a day's first check is a cheap way to confirm a single payment. It stops short of an explicit when-not/alternative statement (e.g. 'for ongoing monitoring use payment_watch').

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