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

Annotations declare readOnlyHint=false and destructiveHint=false, so the agent knows state changes occur; the description usefully discloses that the state change is a credit deduction from a reusable key, which is consistent with the annotations and adds real value. It omits the per-call cost, behavior on insufficient balance, and whether the key is debited on failure.

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?

Two short sentences with no filler, and the primary purpose is front-loaded. It is terse to the point of being fragmented, but nothing is wasted.

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 and a state-mutating, credit-consuming operation, the description should explain what a trust score looks like (scale, format) and what happens when credits run out. Neither is covered, leaving meaningful gaps for a 2-parameter paid 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?

Schema coverage is 50%; the creditKey parameter is already documented in the schema as coming from x402-credit-purchase, and the description only echoes it as a "reusable key." The description does clarify that lookup is a domain, which the bare schema leaves ambiguous, but adds no format or validation detail.

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 phrase "Trust score for a domain" identifies the resource and the outcome, and the second sentence hints at the paid variant by noting credit deduction. But it is a noun fragment with no verb, and it does not distinguish this tool from the sibling trust-api, which appears to serve the same lookup without credits.

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?

There is no explicit guidance on when to use this paid variant versus trust-api or when a creditKey is required rather than optional. The mention of "prepaid credits" implies the precondition, but no alternatives or exclusions are named.

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