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

With no annotations, the description carries the full behavioral burden, but it only discloses the payment model ('5 free trial calls per signed wallet'), implying a signed-wallet requirement. It says nothing about what the lookup returns, error behavior, or what happens after the free calls are exhausted.

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 short and front-loaded, but a meaningful share of its limited space goes to a billing/trial note and a decorative emoji rather than the usage or parameter guidance the definition actually lacks.

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 3-param tool with no annotations, no output schema, and no parameter documentation, the description is far too thin. It neither compensates for the schema gaps nor explains the return value, leaving the agent under-informed.

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?

Three parameters (iso, code, country) have 0% schema description coverage, and the description does not explain their relationship or which one is actually consumed. 'By ISO code' hints at iso/code but leaves 'country' completely unexplained, so an agent cannot tell whether these are alternatives or required together.

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 phrase 'Country by ISO code' names a resource but supplies no verb, so it's ambiguous whether the tool resolves a country from a code or returns a code for a country. It also fails to differentiate from close siblings like x402-country-code or x402-country-brief, which an agent could easily confuse with this one.

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?

There is no when-to-use guidance, no prerequisites beyond the billing note, and no mention of alternatives in the crowded x402-country-* family. The agent is left to infer everything about invocation context.

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