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

Goes well beyond the readOnlyHint/openWorldHint annotations by disclosing that each call costs $0.02 (20000 atomic USDC on Base) and settles via x402 — critical for an agent deciding whether to invoke. It still omits what happens if payment fails or whether a charge is incurred on an unsuccessful probe, so not a 5.

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?

Three short sentences with the capability first and cost/payment second; nothing redundant, and the most decision-relevant facts are front-loaded.

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?

With no output schema, the description should convey what a probe returns (status codes? payment challenges? endpoint list?), and it does not. Cost and payment are covered, but the result shape of this deliberately obscure tool is left entirely to inference.

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% for the single optional `url` parameter, so the baseline is 3. The description adds marginal value by clarifying the no-URL mode means 'up to five catalog endpoints', but nothing about format or validity constraints for the URL itself.

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?

Names a concrete action (probe) and its target (a public URL or up to five catalog endpoints), and the jargon '402 pipe' is at least bounded by the payment sentences. However, '402 pipe probe' is never explained in plain terms, so an agent must already know the x402 protocol to know what a 'probe' actually yields.

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 description implies the two modes (pass a URL vs. scan catalog endpoints), and the schema parameter description explicitly says 'Omit to scan catalog endpoints.' But there is no explicit when-to-use/when-not guidance, no statement of prerequisites (wallet balance), and no named alternative among siblings.

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