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

With no annotations, the description carries the full burden and does so: it states the tool never signs or sends a payment, names the exact price and chain ($0.03 USDC on Base, eip155:8453), documents the 402 challenge/retry handshake, and specifies 400/424 non-charge outcomes. This is unusually complete for a mutation/payment-gated 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 the long check list is dense with distinct evidence rather than filler. It is verbose, but nearly every clause (check names, status codes, pricing) earns its space.

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?

An output schema exists, so return-value structure needn't be explained, yet the description still conveys the 0-100 grading and per-check evidence format, plus the full payment and pricing flow. Nothing an agent needs to invoke it correctly 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?

Schema description coverage is 67%, so most parameters are already documented in the schema. The description only obliquely touches parameters, noting POST-body behavior via 'sent with method POST on every unpaid probe' and the public http(s) 80/443 constraint, without adding format or semantic detail beyond the schema.

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 ('probes an x402-paywalled URL UNPAID ... grades it 0-100 with per-check pass/warn/fail evidence') and enumerates the exact checks performed. It is unmistakable against siblings like read_url or verify_value, which share no domain.

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?

Explains the paid workflow clearly: unpaid calls return HTTP 402 with PAYMENT-REQUIRED and the agent must retry with PAYMENT-SIGNATURE, and it states the three conditions under which no charge occurs. What is missing is any explicit routing guidance against alternative tools, though no sibling overlaps this function.

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