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

With no annotations, the description carries the full burden, and it does disclose non-obvious behavior: paid auth mode and exact cost ($0.003/call via x402 or MPP), plus the POST endpoint. However, it says nothing about behavior on invalid input, error responses, or rate limits.

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 text is dominated by machine-generated metadata (origin URL, hostname, brand, family key, repeated 'Keyword:' lines that restate the same concept five times). The one sentence an agent actually needs is the Summary, which appears mid-block rather than first.

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-param validator with no output schema, the description does state what is returned (area code and city) and covers cost and transport. It stops short of describing error/invalid-number behavior and the exact response shape, which is the main remaining 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?

One required parameter ('value') with 0% schema description coverage, so the schema explains nothing. The description compensates partially by implying the expected input is a landline number in 0xx format, but gives no length, digit-set, or accepted-separator details.

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 landline number (0xx) and report its area code and city.' That is clear and distinguishable from sibling iran_mobile by the 'landline' scope, though the useful sentence is buried under origin/hostname/brand metadata rather than front-loaded.

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 'Use case' lines give concrete scenarios (validate a landline, map 021 to a city, check a region-prefixed fixed line). That is implied usage context, but there is no explicit guidance on when to prefer this over iran_mobile or iran_city, and no exclusions.

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