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

Annotations already declare readOnly, idempotent, non-destructive and open-world, so the safety profile is covered. The description usefully adds the 1-credit cost and what validation is performed. It does not state whether invalid input returns a false flag or raises an error, nor whether extra data such as bank name or BIC is resolved, which matters 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?

A single front-loaded sentence covering both modes with the cost disclosure in a short trailing parenthetical; nothing is padded. The semicolon-joined dual-mode phrasing is dense but readable and would be marginally clearer split into two sentences.

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 no output schema, the description should describe the return shape, and it only hints at it ('split out UK sort code and account'). An agent cannot tell whether invalid input yields an error or a validity flag, nor what additional fields come back. Adequate for a 3-parameter, zero-required tool, but not complete.

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 nominally 100%, but every parameter is described only as 'string', so the schema adds essentially no meaning. The description compensates by mapping iban to the validation mode and sortCode/accountNumber to the format-check mode. However, it supplies no format details such as whether the sort code accepts dashes or how the account number must be padded.

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 and resource and enumerates the actual checks performed (length, structure, mod-97 check digits), plus a clearly distinct second mode: format-checking a UK sort code and account number. An agent immediately knows what the tool does and that it has two operating modes.

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 'or' construction implies the two input paths (IBAN vs. sort code + account number), giving clear usage context. It stops short of explicitly stating prerequisites (e.g. 'supply either iban, or sortCode and accountNumber, not both') or what happens with mixed inputs, so it is clear but not exhaustive.

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