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

Goes well beyond the readOnly/openWorld/idempotent annotations: discloses the per-call price ($0.005 USDC on Base), the exact payment handshake failure mode, and the response shape ('errors, warnings and human-readable prices'). This is precisely the cost/auth/flow context an agent needs before calling an open-world network tool.

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?

Front-loaded with the core action and validation checklist, then payment mechanics, then the HTTP mirror. The long field enumeration is dense but each item specifies real validation behavior; only minor tightening is possible.

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?

No output schema exists, and the description covers what comes back (errors, warnings, human-readable prices), the cost, the failure/retry path, and an alternative transport. Nothing essential for correct invocation is missing.

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?

With 50% schema coverage and an undocumented `method` enum, the description should compensate but doesn't mention `method` at all. It does add meaning the schema omits — the implicit `_meta["x402/payment"]` parameter for payment retry — which is valuable, but half the parameter surface remains unexplained.

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+resource pair ('Probe any public x402 endpoint and validate its 402 challenge') and then enumerates exactly what is validated (version, accepts[], CAIP-2 network, amounts, payTo checksum, EIP-712 extra, Bazaar discovery, /openapi.json). No sibling tool does anything similar, so differentiation is implicit but unambiguous.

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?

Scopes usage to 'any public x402 endpoint' and tells the agent how to complete a paid call: an unpaid call returns the x402 PaymentRequired object, then retry with params._meta["x402/payment"]. It also gives an HTTP alternative (GET /api/x402-lint). No explicit when-not guidance or sibling comparison, but the target context is clear.

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