reply-mail

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

Annotations already establish it as a non-read-only, non-destructive write. The description adds useful behavioral context: "as the signed-in user" clarifies it operates on the user's own mailbox rather than shared mailboxes, and "Requires confirm=true" reinforces the mandatory safety gate. No contradiction with the annotations was found.

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 description is two short sentences with no filler. The core action is front-loaded, and the essential confirmation requirement is stated immediately after. Every word earns its place.

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?

The description is adequate for a simple write operation, and annotations and schema cover safety and parameter meaning. However, it leaves ambiguity about how this tool differs from reply-all-mail and whether the reply is sent immediately or stored as a draft. Given the large sibling set of mail tools, a bit more context would improve completeness.

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%, with all three parameters documented. The description adds no parameter-level meaning beyond the schema, and while the messageId parameter description is generic, the description does not compensate for that gap. Baseline 3 applies because the schema carries the semantic weight.

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 states a specific action and resource: "Reply to a message as the signed-in user." It clearly identifies the operation and the acting scope. However, it does not distinguish from the sibling reply-all-mail, so it stops short of full differentiation.

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?

No guidance is provided on when to choose reply-mail over closely related alternatives like reply-all-mail, forward-mail, or send-mail. The only usage note is "Requires confirm=true," which is a precondition rather than a decision rule among sibling tools. There are no explicit when-to-use or when-not-to-use instructions.

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