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

No annotations are present, so the description carries the behavioral disclosure burden. It adds real behavior: search covers 'every reachable endpoint, not just ones we have bought from,' and results are ordered by proven accuracy, then payment-safety, then price. It does not explicitly say this is a read-only, non-charging operation, but 'searches' plus the later check_before_paying step implies no payment happens here.

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 compact and front-loaded: the 'USE WHEN' trigger comes first, then search behavior, coverage scope, and the required next step. Every sentence contributes actionable guidance, with no filler or repetition.

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?

Given that there is no output schema, the description supplies the most important return context: a ranked, pre-vetted shortlist with ordering criteria. It also closes the loop with check_before_paying. It could state the exact return shape more explicitly, but the combination of schema-covered parameters and workflow guidance is sufficient 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?

Schema description coverage is 100%, so the parameter details are already handled by the schema. The description adds search-ranking context and the next-step workflow, but it does not add extra meaning to parameters like task, max_price_usdc, or allowed_verdicts beyond what the schema already says. A 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 is clear about the action and resource: it "Searches the whole x402 market for what you describe and returns a ranked, pre-vetted shortlist." It does not explicitly contrast itself against sibling tools like rank_sellers or rank_by_accuracy, but its focus on finding payable APIs and the check_before_paying next step give it a distinct role.

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 front-loads an explicit trigger: 'USE WHEN you need an API that does something and want payable options.' It also gives a follow-up workflow: 'Next step: check_before_paying on your pick.' However, it does not state when not to use this tool or whether siblings like rank_sellers should be preferred in other conditions.

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