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

Goes well beyond the annotations: it discloses that the note is stored on our side, visible to the owner in the mail client, invisible to the sender, and that nothing is sent. It also reveals the two-step confirmation protocol and the exact status/action_id/plan_token response shape, which is high-value behavioral context for a mutating tool.

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 tight sentences front-load the purpose and visibility semantics, followed by a clearly labeled CONFIRMATION block. No filler, and the most consequential constraint (proposal-only, confirm_action required) is called out with emphasis.

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 no output schema, the description correctly supplies the return contract (status='confirmation_required', action_id, plan_token) and the prerequisite follow-up call. The only shortfall is the absence of any parameter-level detail for message_id and text.

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 0% and the description adds nothing about the two required parameters — neither the accepted format of message_id (integer or string) nor the constraints or content expectations for text (max 2000 chars). The agent must infer both from the bare schema.

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 ("Attach an internal note to a message") and immediately defines the note's purpose (why it matters, what was agreed, next steps). It also distinguishes the artifact from an outbound reply by noting the sender never sees it and nothing is sent.

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?

The description gives clear context for when a note is appropriate and, critically, explains the confirmation workflow — the tool is only proposed and the write happens via confirm_action. It does not explicitly rule out or route to alternative note-creation siblings, so it stops short of full alternative guidance.

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