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

Annotations already declare readOnlyHint, idempotentHint, and openWorldHint, so safety is covered. The description adds behavioral value by clarifying that validation is against ISO 9362 structure, which signals a syntactic check rather than a registry or existence lookup. This is useful context beyond what annotations alone provide.

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 a single, front-loaded sentence with no filler. It states the action, target, and standard immediately, then adds only the clarifying structural details. Every element 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?

For a single-parameter, read-only validation tool with an output schema, the description is largely sufficient. It captures the validation target and method, while the schema documents the accepted input format. A slightly stronger description might explicitly state that it does not verify BIC existence, but the 'by ISO 9362 structure' phrasing already communicates that reasonably.

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 description already covers the bic format well (8 or 11 characters; spaces/dashes allowed), so the baseline is 3. The description goes further by explaining the semantic composition of a BIC — bank code, ISO country, location, optional branch — which helps an agent understand the input domain beyond raw format constraints.

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 begins with a specific verb and resource: 'Validate a SWIFT/BIC code by ISO 9362 structure.' It names the exact standard and enumerates the structural components (bank code, ISO country, location, optional branch), making it clearly distinct from sibling validation tools like iban_check or luhn_check.

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?

The intended use is implied: use this tool when you need to validate a SWIFT/BIC code. However, the description does not explicitly mention when to prefer this over sibling validators, nor does it state any exclusions or limitations such as 'this only checks structure, not whether the BIC is registered.'

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