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

No annotations are provided, so the description carries the full burden. It usefully discloses the cost ($0.005 per call, USDC on Base) and that it validates, normalizes, and resolves area code to city. But it does not describe the return format, error behavior, or authentication requirements, which are important for a tool with zero annotation coverage.

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?

The description is a single, front-loaded sentence that includes the core action, scope, outcome, and cost. Every element earns its place with no wasted words.

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?

Given the low complexity (one required parameter), rich schema coverage, and no output schema, the description is nearly complete: it states purpose, normalization, area-code resolution, and cost. It could be improved by briefly indicating the return value or handling of invalid inputs, but it is functional as-is.

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% for the single parameter, so the schema already documents that the value is a landline in any common format. The description adds 'Iranian landline number' but does not provide additional syntax, format examples, or constraints 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?

The description states specific verbs (validate, normalize, resolve) and a precise resource (Iranian landline number) with the additional outcome of resolving area code to city. This clearly distinguishes it from siblings like fa_validateMobile and fa_validateBankCard.

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?

Usage is implied by the purpose: use for Iranian landline numbers. However, the description does not explicitly say when to use this versus alternatives such as fa_normalize or fa_validateMobile, nor does it mention prerequisites or exclusions.

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