well-012-x402-probe

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

Annotations already establish read-only, idempotent, non-destructive, open-world behavior, but the description adds substantial operational detail beyond them: hard caps (~12s, 200KB, 5 redirects), the guarantee that no payment occurs, the fact that nothing is stored, and the exact result fields returned. This is rich disclosure for an annotated 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?

The first two sentences are well front-loaded with purpose, cost, behavior, and return fields. However, the tail repeats the same disclaimer three times ('Factual only; as is, no guarantee... Provided as is, with no warranty...'), which is redundant padding that dilutes an otherwise tight definition.

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?

Although there is no output schema, the description enumerates the returned fields (HTTP status, latency, 402 parse, networks, min price, schema flag) and states the operational limits (timeout, size, redirect caps). Combined with the annotations, an agent has everything needed to invoke and interpret results.

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 both parameters (url, method) are already documented in the schema, including the https-only constraint and GET/POST options. The description echoes the 'https only' rule but adds no syntax or format detail beyond the schema, so the baseline of 3 applies.

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 opening sentence states a specific verb (probe), a scoped resource (public https URL), and the target of the probe (x402 payment requirements), with the explicit qualifier that it is unpaid. There are no sibling tools to disambiguate against, and an agent can determine exactly what this tool does from the first sentence alone.

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 clearly frames the use case: checking payment requirements without paying ('Never pays'), and warns it is 'Not a rating or certification,' which implicitly delimits usage. It does not, however, state explicit when-not-to-use conditions or point to an alternative workflow, so it stops short of full routing guidance.

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