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

The description goes beyond the readOnlyHint annotation by explaining important behavioral caveats: the 24h fields cover today so far and reset at 00:00 UTC, the metric is per-facilitator not per-service, and the verification flag transitions from 'listed' to 'on-chain'. This is valuable operational context an agent needs to interpret results correctly.

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 key routing instruction, then packs the return scope, optional parameters, and critical caveats into three efficient sentences. Every sentence adds distinct value without redundancy.

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?

Given the absence of an output schema, the description adequately characterizes the response: settlement volume, transaction counts, time buckets, verification flag, facilitator coverage, and optional timeseries/chain breakdowns. It also covers the most likely misinterpretation (24h semantics) and the service-versus-facilitator distinction.

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 67%, and the description usefully adds meaning by explaining that volume is decimal USD, the optional timeseries is up to 90 days, and the per-chain breakdown is available. It also reinforces the non-trailing meaning of '24h'. Page and per_page are not described, but their pagination purpose is self-evident.

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 states a precise verb and resource: it reports settlement volume and transaction counts per x402 facilitator, and explicitly contrasts this with the service layer. This clearly differentiates it from sibling service-focused tools.

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 opening instruction 'Call this when the question is about the rail rather than the service' gives explicit guidance on when to use it, and 'never per-service' further clarifies the boundary. The sibling tools are service-oriented, so the usage context is unambiguous.

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