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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It reveals the core behavior (format + check-digit validation) but does not disclose what the return looks like (boolean? error object?), edge cases (non-normatted input, unsupported country codes), or whether any network/I-O side effects occur. There is also an unexplained mismatch between 'Provide value' and an empty schema.

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 and the core purpose is front-loaded in the first clause. But the redundant 'Is IBan:' prefix repeats the tool name, and the final 'Provide value' sentence is uninformative and contradictory with the schema — it should have been omitted or clarified.

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?

For a tool with no annotations, no output schema, and an empty input schema, the description is the only source of operational knowledge — and it fails to answer the most basic question: how does the agent supply the IBAN value? Return format, behavior on invalid input, and differentiation from sibling validators are all missing, making the definition inadequate for correct invocation.

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?

While the 0-param baseline would normally be 4, the description actively undermines parameter semantics by instructing the agent to 'Provide value' while providing no parameter, property, or format to carry that value. The description adds no actionable meaning about how input is passed and conflicts with the empty schema, leaving an agent unable to invoke the tool correctly.

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 states a specific verb and resource ('Validate an International Bank Account Number (IBAN) format and check digits'), so an agent can tell this is a validation tool. However, it does not distinguish itself from near-identical siblings (x402-iban-validate, x402-validate-iban), and the trailing 'Provide value' instruction is confusing rather than clarifying.

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?

No guidance is given for when to use this tool versus the two sibling IBAN validation tools (x402-iban-validate, x402-validate-iban) or related validators like x402-is-swift-bic. The bare instruction 'Provide value' is not operational guidance: it never explains how or where the value is supplied, which is especially damaging given the schema defines zero parameters.

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