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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds genuinely new behavioral context: the mutual-exclusivity constraint on input shapes and a preview of the returned standardization fields (useful given no output schema).

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-loads purpose and the either/or rule before the examples. The two inline examples are somewhat verbose but earn their space by demonstrating both input shapes distinctly.

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 output schema, the description compensates by enumerating the returned standardization fields. Covers the essential contract for a 7-param verification tool; only error/failure behavior (invalid address handling) is unstated.

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%, so the baseline is 3; the description adds the cross-parameter constraint that `address` and the component fields are mutually exclusive, plus concrete example values, which is meaning beyond the per-field schema text.

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 (verify) and resource (single US address) plus the value returned (USPS-standardized components, ZIP+4, DPV, county, lat/lon). The 'single' phrasing implicitly separates it from the sibling lob_verify_bulk and lob_autocomplete.

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?

Clearly states the either/or input rule (structured components OR freeform `address`, not both) with worked examples for each form. It does not explicitly name when to prefer lob_verify_bulk or lob_autocomplete, so it stops short of full alternative routing.

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