Resolve a country / state / city to ISO codes (paid $0.002)

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

With no annotations provided, the description carries full responsibility for behavioral disclosure. It explicitly states the tool is paid ($0.002), describes the x402 challenge that occurs without payment, and explains that passing x_payment settles the call. It also notes the bundled dataset has no per-day limits. This gives the agent a complete behavioral model.

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 description is three sentences long, front-loads the cost, and efficiently covers input formats, output details, and the 402/challenge/payment flow. There is no redundancy or fluff; every sentence contributes meaningful information.

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 lookup tool with no output schema, this description is complete: it lists all types of returned data (names, codes, hierarchy, population, coordinates), explains the two input modes, discloses the payment requirement and settlement process, and mentions dataset characteristics. The agent has all necessary context to invoke and interpret the tool correctly.

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?

The schema provides 100% coverage for individual parameters, but the description adds critical cross-parameter semantics: it explains that the free-text 'query' can be used OR the structured 'country/state/city' fields, and clarifies the exact role of 'x_payment' in the payment flow. This goes beyond the schema's per-field descriptions.

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 description clearly states the tool's purpose: 'Resolve a place against a bundled open dataset' and lists specific outputs (ISO 3166-1/-2 codes, hierarchy, population, coordinates). This distinguishes it from sibling validation tools (VAT, IBAN, email, VIN) which operate in entirely different domains.

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 provides clear context for when to use the tool (geographic lookups) and explains the payment workflow. However, it does not explicitly mention when not to use it or name alternatives among siblings. Since the sibling tools are for different validation tasks, the use case is self-evident, but explicit exclusions would earn a 5.

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