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

Annotations already declare readOnly, idempotent, non-destructive and open-world, so the safety profile is covered. The description adds real context beyond them: the address is sent to the Google Address Validation service and nothing else (a privacy disclosure), and 'this creates nothing and mails nothing' reassures about side effects. It stops short of saying what an invalid/unverifiable address yields beyond 'warnings' or whether the call can fail.

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?

Four sentences, front-loaded with purpose, then usage, then scope limits. Each sentence carries information, though 'This creates nothing and mails nothing' partially overlaps with the destructiveHint=false annotation.

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 an output schema present, return values need not be explained, and the safety profile is covered by annotations. The description supplies the remaining essentials: correct usage ordering, the external dependency, and the US-only/complete-address boundary conditions.

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 100% and every nested field (name, line1, line2, state, postal_code) is documented in the schema, so the baseline is 3. The description's 'requires a complete street address' and 'does not look up... from a name' mostly restate the required list plus behavior, adding little syntax or format detail beyond the schema itself.

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 and resource ('Check a US postal address') and describes the outcome ('return it in the normalized form the envelope will be printed with, plus any warnings'), which distinguishes it from every sibling. An agent can tell this apart from create_draft or get_letter_status without opening a schema.

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?

Explicit routing: 'Use this before create_draft whenever the address came from a person rather than from an earlier tool result' names both the alternative and the selecting condition. It also names when-not-to-use by exclusion: no lookup from a name, no non-US addresses.

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