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

Annotations already declare readOnlyHint=true, so the description is not required to restate. It adds valuable context beyond annotations: 'Free' indicates cost, 'live source-backed' implies real-time data freshness, and 'exact x402 prices' highlights precision. No contradiction with 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?

The description is a single sentence, front-loaded with the cost ('Free') and then the core action. Every word contributes, with no filler or 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 tool with only one optional parameter and no output schema, the description covers the essential behavior, cost, and data freshness. It does not explicitly describe the return format, but the action 'find capabilities and their prices' implies a list of matches. Minor gap: no mention of limits or pagination.

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 0%, so the description must compensate. It provides some semantic hint: 'for a goal' suggests the 'query' parameter is the goal to search for. However, no details are given on format, examples, or optionality, leaving the parameter meaning partially under-specified.

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?

Description clearly states the tool's function: 'Find live source-backed capabilities and their exact x402 prices for a goal.' The verb 'find' and resource 'capabilities' are specific and distinguish this from the sibling 'execute_capability' tool.

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 phrase 'for a goal' implies the user should provide a goal to search, but there is no explicit guidance on when to use this over the sibling tool, nor any exclusions. Usage context is inferred rather than clearly stated.

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