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

Annotations already establish readOnly, idempotent, openWorld, so the safety profile is covered. The description adds genuinely new behavior: the validation is structural/ISO 9362 only, and it emits a 'signed XDR-1 receipt', which signals an audit artifact is produced. It does not clarify whether the bank/country are checked against a live registry, which is the one gap.

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?

Three sentences, each earning its place: what is validated, when to run it, and what is returned. The action and the precondition are front-loaded with no 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?

An output schema exists, so return-value detail is unnecessary, and the annotations cover safety. The only remaining question an agent might have — whether a structurally valid but nonexistent BIC would pass — is left unstated, which keeps this just below a full 5.

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%, so the baseline is 3, but the description adds interpretable meaning by decomposing the BIC into bank code, ISO country, location, and optional branch segments, helping the agent understand what each portion of the input represents. It adds no format or syntax detail beyond the schema's own '8 or 11 characters; spaces/dashes allowed'.

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 names a specific verb (Validate) and a specific resource (SWIFT/BIC code) and enumerates the ISO 9362 components checked (bank code, ISO country, location, optional branch). This is clearly distinguishable from sibling validators such as iban_check, lei_check, or gstin_check without opening any schema.

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?

It gives explicit timing and motivation: 'Run before foreign wire transfer dispatch to prevent routing rejection.' That tells the agent when the tool belongs in a workflow. It stops short of naming when NOT to use it or which sibling validator to prefer for a non-SWIFT identifier, so it is not a full 5.

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