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

With no annotations provided, the description carries the full burden of behavioral disclosure, and it discloses nothing beyond the word 'validate.' It does not state the return format (boolean vs. detailed report), whether validation is purely computational or involves network lookups, or how the tool receives an IBAN given that its input schema is empty.

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 description is short but this is under-specification, not conciseness. The duplicated phrase 'Validate IBAN: Validate iban.' contains no information beyond the tool name itself, so no sentence earns its place.

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?

The tool is missing essential context on multiple fronts: how the IBAN is provided (empty schema), what the output looks like (no output schema), when to prefer it over x402-iban-validate or x402-is-iban, and what validation rules apply. An agent cannot invoke this tool correctly based on the available information.

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?

The schema declares zero parameters, and while 0-param tools normally get a baseline of 4, this tool semantically requires an IBAN to validate. The description does not explain how input is supplied (global context, implicit argument, or otherwise), leaving the agent with no way to construct a correct invocation. The description fails to compensate for the schema's silence on input mechanism.

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 'Validate IBAN: Validate iban.' is a pure tautology that restates the tool name in both the title and body without adding any detail about what validation entails, what standards apply, or what the tool returns. It also does nothing to distinguish this tool from the overlapping siblings x402-iban-validate and x402-is-iban, which appear to serve the same function.

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 zero guidance on when to use this tool versus its near-duplicate siblings x402-iban-validate and x402-is-iban, or versus adjacent validation tools like x402-validate-credit-card and x402-bic-lookup. No context, prerequisites, or exclusion criteria are provided.

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