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

Annotations already cover safety (readOnly, idempotent, not open-world). The description adds key behavioral facts beyond them: pricing ($0.05 per successful call, paid over x402 USDC on Base), case- and accent-insensitive name matching, and explicit exclusion of ISO 3166-2 subdivisions.

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?

Front-loaded with the verb and resource. Each of the four sentences earns its place: purpose and returns, name-matching behavior, scope limitation, and price. No filler or redundancy.

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?

Covers inputs, return values (important since no output schema exists), matching semantics, scope, and cost. It omits edge cases such as behavior with multiple name matches or combining code and name, leaving minor gaps for a 3-parameter lookup tool.

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 100% and the schema already defines code, name, and include. The description restates accepted code formats and return fields but adds no new syntax or constraints beyond what the schema provides, so the baseline 3 applies.

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 ('Look up') and resource ('country or territory'), plus exactly what is returned. The scope note 'Country level only: ISO 3166-2 subdivisions are not included' distinguishes it from subdivision tools, but no sibling tool like ref_currency or ref_nuts is named.

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?

No guidance on when to use this tool versus alternatives such as ref_currency or ref_nuts. The description only explains what the tool does, not when it is the right choice.

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