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

Annotations already mark it read-only, idempotent, non-destructive, and open-world. The description goes further: it discloses offline execution, structural-only validation (not a scheme-manager registration proof), pricing, the optional prepaid header, and the absence of wallet/API key requirements. No contradictions with annotations.

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 compact and front-loaded with the core purpose, followed by use case, limitation, and operational details. Each sentence adds value, though the pricing/header details slightly lengthen it. Overall efficient for the amount of information.

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 one required parameter, full schema coverage, an output schema, and annotations covering safety, the description covers everything else an agent needs: what it validates, when to use it, what it cannot prove, and how to call it (pricing and auth). No meaningful gaps remain.

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 fully describes the single parameter (creditorId). The description reinforces it as 'Required input' and clarifies that the tool parses it into country, check digits, business code, and national id, adding meaning about what the input is expected to contain. It doesn't specify a format regex, but the schema plus description are sufficient for a single string parameter.

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 'Validate' and a precise resource 'SEPA Creditor Identifier', and enumerates the exact components checked (country, check digits mod-97, business code, national id). The question format 'Is this Creditor Identifier self-consistent?' adds immediate intent. It is clearly distinct from sibling validation tools like iban_check or bic_check by naming the SEPA Creditor Identifier.

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?

Gives a concrete use case ('Catches mistyped creditor ids before a mandate setup') and a clear exclusion ('Structure only — not a scheme-manager registration proof'). It does not explicitly name alternative tools, but the context plus the offline/structural framing tells an agent when this is appropriate.

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