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

Annotations already establish readOnlyHint=true and idempotentHint=true. The description adds useful behavioral context by saying the surface is 'live' and 'canonical,' implying real-time authoritative data rather than cached or partial information. It does not describe the response structure, but the safety profile is well covered by 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?

A single sentence with no filler. The verb is front-loaded, the resource is specific, and the usage timing is appended 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?

For a zero-parameter read-only tool, the description provides the purpose, resource, and intended usage context. The only minor gap is that it does not hint at what the readiness response contains or how to interpret it, but this is not necessary for correct invocation.

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?

The tool has zero parameters, and the empty schema already documents this completely. With no inputs to explain, the description does not need to add parameter semantics, so the baseline of 4 is appropriate.

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 clearly states the action ('Read') and the resource ('live canonical payment-rail readiness surface'), and adds the timing context 'before attempting a paid call.' This distinguishes it from sibling tools like x402_contract or capability_manifest by focusing specifically on the readiness surface as a preflight check.

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 description explicitly tells the agent when to use this tool: before attempting a paid call. It does not explicitly name alternatives or exclusions, but the use case is clear and sufficient for a zero-parameter readiness check.

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