List endpoints and prices (free)

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

Annotations already declare read-only and open-world semantics; the description adds meaningful details: the operation is free/no payment, it reads from the live /.well-known/x402 manifest, and it returns the current payer mode. These specifics go beyond the annotations and clarify expectations for a live external data source.

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?

Three short sentences front-load the most important fact ('Free, no payment'), then describe the resource and the usage guidance. Every sentence adds distinct value: cost, content, and workflow.

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?

Even with no output schema, the description clearly states the response contains total count, matches, and current payer mode. It also explains the source of truth and how to use the result before genesis402_call, making it complete for a simple one-parameter catalog 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 single optional parameter is fully documented in the input schema, including matching behavior and examples. The description adds no additional parameter-level semantics beyond what the schema already provides, so the baseline score of 3 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 uses the specific verb 'Lists' with a well-defined resource: every Genesis402 endpoint from the live x402 manifest, enumerating the exact fields returned (name, HTTP path, USD price, title, parameter schema). It also distinguishes itself from genesis402_call by positioning the catalog as the discovery step before calling endpoints.

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 instructs the agent to 'Call this first to find the right endpoint name and parameters for genesis402_call,' making the intended workflow clear. It doesn't spell out when not to use it or name alternative discovery tools, but the guidance is sufficient given the sibling context.

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