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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds real substance beyond that: what is being validated (22 digits, both check digits) and that the identifier decomposes into bank, branch and account segments. It stops short of saying what a failed check returns.

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?

One sentence, zero filler, with the resource and its defining constraints front-loaded. Nothing is repeated for padding.

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 one-parameter validator with no output schema, the description covers the input constraint and hints at the returned decomposition (bank, branch, account). Missing only the outcome semantics – what an invalid CBU returns and whether components are always present – which is a modest gap for a tool this simple.

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?

With a single parameter at 100% schema description coverage, the schema already carries the burden and states 'The CBU or CVU, 22 digits.' The description restates the same 22-digit constraint and adds the check-digit notion, so it neither adds much nor leaves a gap.

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 (check) and a specific resource (Argentine CBU or CVU), with the format constraints that define the resource. The 'Argentine' qualifier implicitly separates it from iban_checker and the other identifier checkers in the sibling list, though it never names them.

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 is only implied by the verb 'check' – an agent can infer this validates an identifier, but the description never says when to reach for it over iban_checker or swift_code_checker, nor what to do with an invalid result.

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