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

With no annotations provided, the description carries the full disclosure burden and does so well: it states the per-call cost, clarifies that only validity is returned, and explicitly rules out database lookup and personal data exposure. That is exactly the behavioral context an agent needs before calling this 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?

Two compact sentences front-load the cost, then state purpose and behavioral boundaries. Every sentence adds useful information with no repetition or waste.

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 format-validation tool with full schema coverage, the description is complete enough to call correctly. Since there is no output schema, it appropriately states that the return is validity only.

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 the schema already documents both parameters and the type enum. The description lists the supported identity types, which aligns with the enum but does not add format details such as digit length or pattern expectations for each type. Baseline 3 is appropriate.

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, 'Format-validate', and a precise resource set: Nigerian NIN, BVN, TIN, CAC RC, and CAC BN numbers. It clearly distinguishes this tool from sibling validation/lookup tools by emphasizing format validation rather than database lookup.

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 description makes the use case clear: format validation only, with no database lookup and no personal data returned. It does not explicitly name alternatives such as ng_bank_validate or ng_phone_lookup, but the intended context is still clear.

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