validate_postal_code

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

Annotations already provide readOnlyHint and idempotentHint, indicating safe and idempotent operation. The description adds value by specifying the return structure (valid, postal_code, country, format) and listing supported country formats, which goes beyond what annotations provide. No contradictions.

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 concise and packs necessary information (supported countries, formats, use cases) into a single paragraph. It could be slightly better structured (e.g., bullet points for countries) but is efficient and front-loaded with purpose.

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?

Given the complexity of multiple country patterns, the description covers purpose, parameters, output structure, and use cases thoroughly. The output schema is mentioned, and annotations handle safety. No gaps remain for an agent to select and invoke this 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?

Schema coverage is 100%, but the description adds significant context: example postal codes for various countries, clarification that country_code is two-letter ISO, and details of the return format. This enhances understanding beyond the schema alone.

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 validates postal code format for European countries using official patterns, lists supported countries and formats, and mentions use cases (e-commerce, address verification, logistics). It distinguishes itself from sibling validation tools like validate_iban or validate_nif by focusing specifically on postal codes.

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 implies usage through listed supported countries and example use cases, but does not explicitly state when to use versus alternatives or when not to use. However, given the specificity of postal code validation, the guidance is clear enough for an agent.

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