x402 facilitator volumes

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

Annotations already mark readOnlyHint=true, so the description isn't required to state that. However, it adds substantial behavioral detail: the on-chain verification flag, the meaning of 'listed' vs 'on-chain', the exact definition of *_24h fields (today UTC so far, not trailing 24h), and that volume is decimal USD. No contradiction with annotations.

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 description is front-loaded with the trigger condition, then the return payload, then optional features, then caveats — a logical flow. Every sentence carries information; the caveats are essential and not redundant. It's longer than a single sentence but earns its length.

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 read-only data tool with no output schema, the description covers the key output elements (volume, counts, verification flag, timeframes), the units, the optional breakdowns, and the critical temporal caveat. An agent has enough to invoke it correctly and interpret results. Nothing crucial 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 covers 67% of parameters (4 of 6 have descriptions). The description reinforces include_timeseries and include_chains by calling out 'optional daily timeseries (up to 90 days) and per-chain breakdown', and it reiterates the critical timeframe nuance ('prefer 7d'). While page/per_page lack descriptions in both, they are conventional pagination parameters. The description adds meaningful clarification beyond the schema for the most important params.

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 opens with a precise trigger condition — 'question is about the rail rather than the service' — and names the exact resource (facilitator settlement volumes) and the data returned (volume and tx counts per facilitator). This clearly separates it from sibling tools like x402_search_services or x402_get_service, which target services.

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 explicitly states when to call ('about the rail rather than the service') and what not to do ('never per-service'), plus a strong caveat to prefer 7d over 24h due to reset semantics. While it doesn't name specific alternatives, the per-service/per-facilitator distinction is sufficient routing guidance.

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