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

With no annotations, the description carries the full burden and does add genuinely useful behavioral context: the per-call cost ($0.005) and the payment rail (USDC on Base). However, it says nothing about what 'validate' means operationally (format-only vs. check-digit algorithm) or how invalid input is reported, so meaningful behavioral gaps remain.

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 compact sentence, front-loaded with the action and resource, followed by the format and pricing in a tight parenthetical. No sentence is wasted and nothing important is buried.

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 one-parameter validator this is nearly complete, but with no output schema the description never tells the agent what a validation call returns (boolean, valid/invalid payload, error shape). That single omission keeps it from being fully self-sufficient.

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?

There is a single parameter with 100% schema description coverage, so the schema already documents 'value' as a 12-digit economic code. The description's '(کد اقتصادی, 12 digits)' restates that constraint without adding syntax or edge-case detail, matching the baseline 3 when schema does the heavy lifting.

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 a precisely named resource ('Iranian economic code', کد اقتصادی) with the 12-digit format constraint. This clearly distinguishes it from siblings such as fa_validateNationalId, fa_validateCompanyId, and fa_validateSheba without needing to open any 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?

The description gives no indication of when to use this tool versus the other validators, nor any prerequisites or exclusions. It only describes what the tool validates, leaving the agent to infer usage context from the name alone.

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