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

Annotations only say destructive and idempotent; the description goes well beyond them by disclosing the 30-day forwarding window, that it cannot be extended, that the old address cannot send or be reverted, and that billing stops in the meantime. It also adds a prompt-injection warning about untrusted message content, which is real behavioral context for an agent.

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 core operation and its irreversible 30-day consequence are front-loaded, and every clause carries information. It is dense but long, and the trailing untrusted-content paragraph, while useful, is somewhat tangential to the operation itself.

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 and annotations covering safety hints, the description supplies the remaining essentials: irreversibility, time limit, tenant restriction and the need for user confirmation. Nothing an agent needs before invoking this destructive move is missing.

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% and both parameters already document that they accept an id, address or external id, so the description adds little. It only restates the framing of old vs new mailbox, which is the baseline expectation when the schema does the work.

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 concrete verb and resource: move a hosted address to a mailbox on your own domain. That is clearly distinct from siblings such as create_mailbox, delete_mailbox and forward-related list tools, so an agent can pick it without opening the 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?

Gives clear preconditions and an explicit instruction to confirm with the user first, plus the constraint that the target must be in the same tenant. It does not name a sibling alternative (e.g. create_mailbox) for the non-moving case, so it stops short of a 5.

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