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

No annotations provided, so description carries full burden. It discloses the payment behavior (paid terms flow), what each view does, and the validation algorithm (length + mod-97). Does not mention error/rate limits, but this is substantial for a validation tool.

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?

Four sentences, each with distinct value: validation method, view behaviors, payment flow, and pricing alternative. No filler, front-loaded with purpose.

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 3-param tool with no output schema, the description covers the main operations and the complex paid workflow. It doesn't describe return structure, but that's not essential without an output schema. Sibling context makes selection easy.

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%, baseline 3. Description adds meaning to view enum ('decode' resolves parts, 'format' returns electronic/paper forms) and explains x_payment flow in greater detail than the schema. iban param not elaborated, but schema already says spaces optional.

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 specific operation: 'Validate an IBAN (length + mod-97 check digits)' and describes two distinct views (decode, format). Clearly identifies the resource (IBAN) and differs from sibling validation tools (email_check, phone_check, etc.).

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?

Provides clear workflow for paid calls: call without x_payment to get terms, sign, then call again with x_payment. Also points to the free `pricing` tool for all prices. Does not explicitly name alternative IBAN tools, but siblings are clearly different resources.

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