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

Annotations already cover readOnly/openWorld, and the description adds real value beyond them: it discloses pricing ($0.005 after shared free calls) and the critical caveat that it cannot certify safety. It stops short of describing evidence sources or how the score is computed, so it is strong but not exhaustive.

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?

Sentences are dense but each carries load: scope, limits, price, alternative, and boundary are all front-loaded. The 'x402 API endpoints: x402_merchant_trust_check' fragment is the one piece that adds ambiguity rather than clarity, since it collides with an actual sibling tool name.

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 an output schema present and annotations covering the safety profile, the description only needed to add scope, cost and caveats — which it does. The remaining gap is the confusing reference to an 'x402 endpoint' that shares a name with a sibling tool, which could make an agent question whether it is calling the right one.

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 each parameter (domain, context, merchant_wallet_or_id, transaction_amount_usd) already carries its own description. The description adds no format or interpretation guidance beyond restating that the call does not authorize a purchase, which the schema already says — baseline 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 description names the specific resource (public trust evidence for an unfamiliar online shop) and enumerates exactly what the tool returns: evidence score, risk flags, missing signals and limits. It also distinguishes itself from b2b_vendor_stability_evaluator, so an agent can differentiate it from siblings without inspecting schemas.

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?

It gives an explicit positive condition (consumer purchase from an unfamiliar shop) and an explicit alternative for the other case (B2B supplier procurement → b2b_vendor_stability_evaluator). It also states a hard boundary: it does not buy goods or authorize payment.

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