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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), so the description focuses on the value-added disclosure: the confidence tiering (high/medium/low), the presence of data_version and sources, and an explicit disclaimer about what validation does not prove. This is meaningful behavioral context an agent cannot infer from 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?

Front-loaded with the validation scope, then the example, then the response contract. The response sentence is dense and parenthesis-heavy but every clause carries interpretive value; nothing is filler.

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 an output schema present and full annotations, the description needs little more, and it usefully explains the confidence tiers that a bare schema would not convey. The only mild redundancy is enumerating response fields that the output schema already declares.

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?

Only one parameter, and the schema already documents it fully (100% coverage) including the 8-or-11-character format and the 'EBILAEAD' example. The description repeats the same example rather than adding new constraint detail, so baseline 3 applies.

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 resource (BIC, ISO 9362) and enumerates the sub-checks performed: structure, country code, test-BIC flag, bank and branch parts, and bank name lookup. This is clearly distinguishable from siblings such as validate_iban, validate_phone, and validate_postal_code by resource alone.

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?

Usage context is clear from 'structural validation only — never proof that an identifier is issued or belongs to someone,' which tells the agent the limits of what the tool answers. It does not explicitly name an alternative or exclusion, but sibling names make the routing obvious.

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