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

With no annotations, the description carries the full behavioral burden defense disclosure. It explicitly discloses that the call is public, keyless, live, and returns 402 payment details. It does not mention side effects or error cases, but for a quote-style read operation these are minor gaps.

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?

Two sentences with no filler, front-loading the core behavior and access model. Every clause earns its place.

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 simple two-parameter public tool, the description plus fully documented schema gives enough to call it correctly: purpose, access requirements, target selection, and return content. It only lacks explicit sibling differentiation and detail on non-402 outcomes.

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 schema already documents both `tool` and `serviceId`. The description adds only that the call targets a registry tool and does not meaningfully clarify parameter interaction 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 states a precise behavior: invoke the registry tool without authentication and return the live 402 payment requirements (price/payTo). This clearly differentiates it from siblings like pay_service (which pays) and list_services (which lists), even though no sibling is named explicitly.

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 gives useful context by saying the call is public and unsigned, implying it should be used to discover payment requirements before paying for a service. However, it does not name alternatives or state when not to use this tool, so the agent must infer the routing decision.

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