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

No annotations, so the description carries full burden. It usefully discloses the lookup mechanism (fixed table), the matching mode (substring), the failure behavior ('unknown country returns ok false'), and the payment model (5 free trial calls per signed wallet). It does not describe the shape of a successful response beyond 'ISO language codes,' leaving output structure opaque.

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?

A single front-loaded sentence delivers purpose, mechanism, and the failure case efficiently. The trailing trial-call/emoji tag is minor promotional noise but does not obscure the core content.

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?

With no annotations and no output schema, the description must stand alone and does cover the input domain, matching behavior, and error contract. It falls short on disambiguating the two undocumented parameters and on describing the successful return payload (e.g., single code vs list).

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 coverage is 0% and neither 'name' nor 'country' is documented. The description only implies a country-name input, and the existence of a separate 'name' parameter alongside 'country' is never explained, leaving an agent guessing whether 'name' is a language name, an alternate country field, or something else.

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 and resource: 'Returns ISO language codes for a country name.' An agent knows the output type and input domain. However, it does not distinguish itself from close siblings such as x402-language-name, x402-country-code, or x402-country, which appear to occupy the same lookup space.

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 explains mechanism ('fixed table and substring matching') but never states when to prefer this over x402-language-name or x402-country-code. No prerequisites, no exclusions, no alternative routing.

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