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

No annotations are provided, so the description carries the full behavioral burden. It does disclose cost and payment rail ($0.005 per call, USDC on Base) and the validation method, but it never says what happens on a failed Luhn check (error vs. false), whether the issuing-bank lookup can fail independently, or whether any auth is required.

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, front-loaded with the action and resource, with the cost detail trailing. No filler or redundant restatement of the tool name.

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?

There is no output schema, and the description does at least state the primary return (issuing bank), which is the key missing piece for a validator. However, it omits the failure semantics of an invalid card and any indication of the response shape, leaving a real gap for a validation tool with no annotations.

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 documents '16-digit Iranian bank card number'. The description reinforces the domain (Iranian PAN, Luhn-checkable) but adds no format, normalization, or edge-case detail beyond the schema.

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 (validate) and resource (Iranian bank card / PAN) and adds the mechanism (Luhn check digit) plus the output (issuing bank). This clearly separates it from sibling validators such as fa_validateNationalId, fa_validateSheba, and fa_validatePostalCode.

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 gives no when-to-use guidance, no conditions for selecting it over the other fa_validate* tools, and no exclusions. The only additional context is pricing, which is not usage guidance.

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