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

The annotations already declare this as a safe, idempotent, non-destructive, non-open-world read, so the safety burden is lifted. The description adds a genuinely useful behavioral nuance beyond the annotations: the PMB number only exists after USPS Form 1583 verification, implying the value may be pending. It stops short of stating what is returned when verification is incomplete, but the output schema covers return shape.

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 what the tool returns and follows immediately with the routing rule, which is the right ordering. However, the second sentence is a run-on and repeats 'from addresses the operator already uses' twice, a redundancy that could be trimmed without loss.

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 described. Annotations carry the safety/idempotency profile, there are no parameters to document, and the description supplies the two things structured data cannot: the USPS Form 1583 gating caveat and the sibling routing rule.

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 tool takes zero parameters, so there is nothing for the description to disambiguate and the baseline is 4. No misleading or missing parameter guidance is present.

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+resource ('Get your agent's real mailing address') and enriches it with concrete detail: street address plus PMB at the Manhattan Beach, CA facility. It also names the sibling it is not (list_inbound_forwarding_addresses), so an agent can route correctly without opening either 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?

Explicitly gives the alternative and the condition that selects it: inbound context from operator-used addresses goes to list_inbound_forwarding_addresses instead. The agent knows both when to use this tool and when to switch, with no inference required.

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