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

With no annotations, the description carries the burden and does disclose meaningful behavior: it validates by recomputing the check digit, returns validity plus parsed digits, and even states cost ($0.005/call, USDC on Base). It omits how malformed/non-11-digit input is handled and any rate/permission constraints, but covers more than most.

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?

Purpose is front-loaded in the first clause, followed by usage and return info; every sentence carries weight. It is slightly dense with the added pricing parenthetical, but no real 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 single-parameter validator with no output schema, it explains what is checked, how, what is returned, and the cost. Only the invalid-input/error behavior is left unspecified, which for a pure validator is a minor gap.

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 100% and the single 'value' parameter is already documented as '11-digit legal-entity national ID'. The description restates the same 11-digit constraint, adding no format or syntax detail beyond the schema, so baseline 3 applies.

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), a precise resource (Iranian company national ID / شناسه ملی اشخاص حقوقی), the mechanism (recomputing its check digit), and scope (the 11-digit legal-entity identifier). The 'legal-entity' framing distinguishes it from the personal-ID sibling fa_validateNationalId without needing the schema.

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?

Gives a clear usage context ('when onboarding a business customer or validating an Iranian legal entity'), which is helpful. However, it never names the alternative (e.g., fa_validateNationalId for individuals vs this for companies) or states when not to use it, leaving sibling disambiguation to inference.

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