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

No annotations are provided, so the description must carry the full behavioral burden, and it does disclose auth mode (paid) and price ($0.003/call via x402 or MPP), which are important pre-invocation facts. 'When recognised' also signals that unrecognized codes may yield only a validity result, though error/rate-limit behavior remains unstated.

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 entry is bloated with origin URL, hostname, brand, provider aliases, family key, endpoint, and four keyword lines, and the Summary/Source description repeat each other verbatim. The actual purpose is not front-loaded but buried after infrastructure metadata.

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 validation tool with no output schema and no annotations, the description covers purpose, input format, payment/auth, and the general shape of the result (province and city on success). Only edge-case return behavior is left implicit, which 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?

With 1 parameter at 0% schema description coverage, the description must compensate and does add the key constraint ('10 digits') beyond the bare string type. However, it gives no example format and doesn't say whether Persian digits are accepted, so coverage is partial.

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 Summary line states a specific verb and resource: 'Validate an Iranian postal code (10 digits) and, when recognised, report the matching province and city.' That is specific enough to separate it from siblings like iran_city or iran_province, though the useful statement is buried under origin/hostname/family-key metadata.

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?

Three concrete use cases ('validate a postal code and tell me the province', 'check a کد پستی before shipping', 'confirm a 10-digit postcode is valid') give clear context for when to call it. There is no explicit exclusion or named alternative versus sibling tools, so it stops short of a 5.

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