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

Annotations declare a non-read-only, idempotent, non-destructive mutation, and the description enriches that with the full lifecycle: the draft remains in Drafts unsent and editable, the assistant sees it via list_pending_approvals, approve_and_send files the Sent copy and removes the draft, and invalid uids are refused. This adds state-transition and side-effect detail well beyond the annotation flags.

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?

Purpose is front-loaded in the first sentence, followed by usage condition, lifecycle, and failure behavior in a compact block. It is somewhat long, and the closing note about there being no 'send back for changes' tool is tangential, but each sentence carries actionable content.

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?

For a single-parameter mutation with no output schema, the description supplies everything needed: when to call it, what state results, who acts next, how the state resolves, and what input is rejected. No annotation or schema gap is left uncovered.

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% with a single uid parameter, so the baseline is 3. The description adds a genuine constraint the schema does not encode: the uid must identify a draft in the Drafts folder or the call is refused, which sharpens valid-value selection beyond 'UID of the draft'.

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 ('Mark a draft ... as waiting for approval') and immediately scopes it relative to siblings, naming the drafting tools it follows and the downstream tools (list_pending_approvals, approve_and_send) that consume the state. An agent can distinguish this from draft_* and send_email without opening any 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 explicit when-to-use conditions: after draft_reply/draft_forward/draft_email, when the user cannot send from this mailbox or wants owner review. It also names the alternative path (owner replies manually) and the failure boundary (refuses non-Draft uids), so routing is unambiguous.

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