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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered; the description adds the non-obvious fact that this call is free while the listed tools are paid, and it discloses the shape of the returned payload. It omits response format/pagination details, but for a zero-param read that is a minor gap.

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 the cost qualifier front-loaded and the return contents listed compactly. No filler, nothing redundant with the schema or annotations.

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?

With no output schema, the description carries the burden of describing returns and does so by enumerating price, input schema, example, and endpoint. It does not specify the serialization format or ordering of the list, which is the only remaining gap for an otherwise complete free discovery tool.

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 takes zero parameters, so the baseline is 4; there is no parameter semantics for the description to clarify or for the schema to omit.

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 specific verb+resource ("Lists every paid tool on this server") and enumerates exactly what each entry contains: USDC price, input schema, example input, and the equivalent x402 HTTP endpoint. That is enough to distinguish it from every kr_* sibling, which are domain-data tools rather than a service catalog.

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 leading "Free." signals the cost distinction against the paid tools it lists, which is genuine usage context, but the description never states when to call it (e.g. before invoking a paid tool to discover prices) or any exclusion. Usage is only implied by the tool's nature as a discovery endpoint.

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