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

With no annotations, the description carries the full burden and does it well: it declares a non-destructive read-only audit ('Never sends a payment'), discloses the per-call cost and payment mechanism ('$0.01 USDC per call via x402'), and describes the return shape (score, verdict, ordered fix list).

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 core statement is front-loaded and dense with useful specifics, but the appended example output JSON is truncated mid-object ('"severity"'), which wastes space and gives an incomplete illustration rather than a clean one.

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 no output schema, the description supplies the output structure and an example, plus cost and side-effect disclosure — nearly everything an agent needs. The truncated example is the only shortfall.

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 100% with only two parameters, both fully described in the schema (url purpose, method enum), so the schema does the heavy lifting. The description adds no syntax or format detail beyond restating that it audits an x402 endpoint URL.

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?

States a specific verb and resource ('Audits any x402 endpoint URL') and enumerates exactly what the audit covers: readiness check, 500-char description limit, Bazaar listing, OpenAPI x-payment-info, 402 Index, favicon, llms.txt, /.well-known/x402. This is clearly differentiated from the narrower sibling x402_endpoint_check.

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 opening question 'Will my paid API get listed?' frames the use case precisely, and 'Never sends a payment' removes a likely hesitation. It does not, however, explicitly name x402_endpoint_check as the lighter-weight alternative when only a readiness check is needed.

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