Verify a postal address against authoritative postal data

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It states the return values (verification level, corrected address, persistent identifier), discloses a limitation (cannot confirm newly built addresses), and interprets results ('not confirmed' means unknown, not fabricated). It also warns against misinterpreting verification as evidence of person association. This is thorough transparency.

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 comprehensive yet efficient. It opens with the core function, then covers return values, usage guidance, and important limitations without redundancy. Every sentence contributes to the agent's understanding, making it well-structured and appropriately sized for the tool's complexity.

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?

The tool has no output schema, and the description compensates by naming the three return components (verification level, corrected address, persistent identifier). It also covers usage, limitations, and interpretation. However, it doesn't describe the specific response structure or possible verification levels, which would be useful for full completeness. Overall, it provides sufficient context for correct invocation.

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 description coverage is 80%, so the schema already documents most parameters. The description does not add parameter-specific semantics beyond the schema's descriptions; it only mentions 'using maintained postal reference data,' which pertains to data source rather than parameter meaning. This aligns with the baseline of 3 for high schema coverage.

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 identifies the tool's function with a specific verb and resource: 'Checks whether a postal address exists and is deliverable.' It is unambiguous about the resource type, which inherently differentiates it from siblings like verify_email and verify_phone. However, it does not explicitly name or contrast itself against sibling tools, so it falls short of full explicit differentiation.

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 explicit when-to-use guidance ('Call this before any action that depends on an address being real: shipping, billing, account creation, or writing an address to a system of record') and explicit when-not-to-use guidance ('Do NOT use this to look up who lives at an address, and do not treat a verified address as evidence that a particular person is associated with it'). It covers both positive and negative use cases clearly, even though it doesn't name alternative tools.

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