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

Annotations already declare idempotency, non-destructiveness and open-world reads, so the description's job is to add side-effect context, which it does well: the stablecoin leg is chain-verified, the figure is measured against an independent reference and against what was routed, and every later route on the pair inherits it as a measured payment. The recurring-cycle closure is a genuinely non-obvious behavioral trait. It stops short of covering permission requirements or what happens on a duplicate/invalid tx hash.

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?

The core action is front-loaded in the opening clause and the whole definition is a single dense paragraph with no filler. Some wording restates schema semantics ('what left (source currency) and what arrived (destination currency)'), and the long compound sentence makes it slightly heavy to parse, but nothing is expendable.

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 7-parameter write tool with one required field, full schema coverage and no output schema, the description covers trigger, data semantics, chain verification, downstream measurement effects and the recurring edge case. No output schema exists, so the absence of return-value documentation is not a gap here.

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 description coverage is 100%, so the baseline is 3; the description still adds value by framing sent and landed as the source-side and destination-side amounts against the intent rather than leaving them as bare numbers. The closing constraint 'amounts only, never names or account numbers' is semantic guidance no schema field carries. It adds meaning but does not explain the settled_at or provider defaults beyond what the schema states.

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?

The description uses a specific verb+resource: it closes a payment once funds have arrived, against a remembered intent, recording what left and what landed, with an optional stablecoin leg keyed by chain and tx hash. An agent can tell this is a settlement-recording write rather than a quote or verification tool. It does not name a sibling (e.g., confirm_payment, reconcile_payment, record_release) to sharpen the boundary, so it falls short of a 5.

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?

The trigger condition is clear: use it once the money has actually arrived, and it references route_intent's remembered.intent_id as the input source. The recurring-intent case is explicitly scoped (closes the current cycle only, series advances to next due date). What's missing is an exclusion sentence pointing to the sibling that handles the case where money has not yet landed or when reconciling a discrepancy.

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