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

With no annotations, the description carries the full load and does well: it states the probe is non-paying ("Never pays"), discloses the price ($0.005 USDC via x402), the default GET-then-POST fallback on 404/405, and the ready/needs_fixes scoring output. It omits failure modes such as behavior on network timeouts or non-402 responses beyond the verdict.

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 purpose and usage are front-loaded, which is good, but the description then crams every reported field into a long comma list and appends an example output that is truncated mid-token ("amou"), which is dead weight rather than illustrative.

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?

There is no output schema, so the description correctly takes on the burden of describing the return value: verdict, 0-100 score, issue list, and per-field report contents. The truncated example and missing detail on error/timeout responses keep it just short of complete.

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% and both parameters are already documented in the schema, so the baseline is 3. The description reinforces the probing semantics but adds no syntax or format detail (e.g., URL normalization, allowed redirect counts) beyond what the schema states.

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 action (probe a paid API URL for x402 readiness) plus the exact artifact returned: a valid 402, requirement location, network, asset, price, payTo, and a ready/needs_fixes verdict. An agent can immediately distinguish this from siblings like x402_seller_audit or url_dossier.

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?

"Use before listing an endpoint or paying it" gives clear triggering contexts and implicitly contrasts with actually paying. It does not explicitly route the agent to the closest alternative (x402_seller_audit) when a seller-side audit is what's wanted, so it falls short of a 5.

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