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

Goes well beyond the annotations: it discloses the $1.00 USDC per-call price, that payment happens inside the tool call via x402, that failures are not charged, and that nothing is signed or paid against the target. This is exactly the cost and side-effect context an agent needs before spending money. Minor tension worth noting: readOnlyHint=true coexists with a per-call wallet charge, though the tool is read-only with respect to the checked endpoint.

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 question, then the check list, then cost and safety. One long sentence enumerating checks is dense but each clause names a distinct verification, so little is wasted; the pricing sentence could be tightened.

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 compensates by listing what is verified, which implies the shape of the result, but it never says whether the response is a pass/fail per check or a single verdict. Cost, safety, and scope are otherwise fully covered for a one-parameter tool.

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?

There is a single parameter with 100% schema description coverage ('Public https URL of the paid endpoint'), so the schema already carries its meaning. The description adds no format or constraint detail beyond it (e.g., https-only enforcement is only implied by 'Public https URL' in the schema). Baseline 3 applies when the schema does the work.

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 (a 402 conformance check of an x402/MPP paid endpoint) and frames the exact question it answers: can buyer agents' SDKs pay it? The enumerated checks (v2 requirements, malformed payment refusal, MPP challenge, live price) make it clearly distinct from siblings like check_offer, certify_offer, and lint_listing.

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 scopes applicability well: it applies to x402 v2 or MPP endpoints and works on unpaid requests only, with failed calls not charged. It does not, however, explicitly route the agent away from near-neighbors such as check_offer or certify_continuous, nor state prerequisites like the endpoint being publicly reachable over https.

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