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

Annotations already declare readOnlyHint=true and idempotentHint=true, so the safety profile is clear. The description adds the beta-access restriction and 'approved accounts' context, which is valuable behavioral information not present in the annotations. It does not explain what happens if beta access is missing, but this is a minor gap.

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?

Two sentences: first states the tool's purpose and access requirements, second provides an alternative. It is front-loaded, free of redundancy, and every sentence serves a distinct function.

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 zero parameters, a documented output schema, and clear annotations (read-only, idempotent), the description fully covers usage context. It also notes the beta access constraint and alternative tool, making it complete for practical decision-making.

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 has zero parameters, so the description need not elaborate on parameter details. The baseline for 0 parameters is 4, and no additional parameter explanation is needed.

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 retrieves the agent's real mailing address (street address + mailbox number) for beta-approved accounts, and explicitly distinguishes it from the sibling list_inbound_forwarding_addresses tool by noting that tool returns a private intake alias for general inbound context.

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?

Provides explicit when-to-use guidance: use this tool only for the beta mailbox address, and for generally available inbound context, use list_inbound_forwarding_addresses instead. This directly addresses alternative selection.

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