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

Annotations already declare readOnlyHint=true and destructiveHint=false, lowering the bar, and the description goes beyond that by disclosing a concrete workflow detail: the forwarding confirmation code exists specifically to be entered into Gmail's settings. What it omits is failure modes (e.g., behavior when forwarding is not yet set up or the mailbox is missing).

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?

A single front-loaded sentence that opens with the verb+resource and then enumerates outputs. The trailing parenthetical about Gmail's settings is worth its length, though the sentence is dense enough that it borders on overloaded.

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?

No output schema exists, so the description carries the return-value burden and does enumerate the key fields, including the nested forwarding.confirmationCode. It lacks the mailbox-not-found/failure semantics, but for a single-param read tool it is close to complete.

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?

With schema description coverage at 100% and only one parameter, the schema already documents mailboxId and even its source (add_support_email or get_setup_status). The description adds no syntax or format detail about the id, so baseline 3 applies.

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 ('Read one support mailbox') and enumerates the returned fields (supportAddress, inboundAddress, forwarding status, forwarding.confirmationCode). It does not explicitly contrast itself with the sibling add_support_email or get_setup_status, but the read-one contract is unambiguous.

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?

Usage is only implied: it is a getter for a single mailbox. The description does not state when to reach for this versus add_support_email (write) or get_setup_status, nor does it name exclusions. Adequate but leaves the routing inference to the agent.

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