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

With no annotations, the description carries the full behavioral burden and does well by disclosing cost per call, the check-digit algorithm, and the critical limitation that this is format validation only. It does not explicitly confirm read-only behavior or describe the response shape.

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 short sentences with no wasted language. Cost, purpose, and the key limitation are front-loaded and easy to scan.

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 simple two-parameter validation tool with a fully described schema, the description covers purpose, cost, and the main limitation. Because there is no output schema, it could be stronger by stating what the validation result looks like.

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 description coverage is 100%, so both parameters are already documented in the schema. The description restates the 10-digit account number and 3-digit bank code formats but adds no extra parameter semantics such as bank code lists or error conditions.

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 states a specific verb and resource: validate a 10-digit NUBAN account number against a 3-digit CBN bank code using the check-digit algorithm. This is clearly distinguishable from the sibling chain_* and ng_* tools.

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 a clear usage boundary: format validation only, and explicitly warns that it does not confirm account existence. It does not name an alternative tool for existence checks, so it falls short of full when/when-not/alternatives guidance.

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