Create a draft

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

Beyond the annotations, the description discloses that nothing is sent, that an empty draft is legal, and that the return value includes the draft id plus underlying message id/threadId. It also explains the safe workflow of draft-then-send. This gives the agent an accurate behavioral model for a write action.

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 four sentences, front-loaded with the core purpose and non-sending guarantee, then optionality, reply recipe, return value, and usage routing. Every sentence contributes actionable information without redundancy or fluff. The structure makes it easy for an agent to scan.

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 draft-creation tool with nine optional parameters, no output schema, and no destructive/read-only annotations, this description is complete. It covers purpose, side effects, parameter relationships, return value, required follow-up tools, and when to prefer this tool over send_message. An agent can invoke it correctly without needing additional context.

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?

The schema already provides 100% parameter coverage with descriptions for every field, so the baseline is 3. The description adds meaningful guidance beyond the schema by clarifying that all fields are optional and by providing the reply-draft pattern for thread_id, in_reply_to, and subject. It does not elaborate on cc/bcc/body fields, but the schema already handles those adequately.

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 operation: creates a draft email in the mailbox without sending. It differentiates from related tools by explicit no-send behavior and by naming the draft id consumers (update_draft/send_draft/delete_draft). The purpose is unmistakable even 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?

The description explicitly tells the agent when to use this tool over send_message: draft first and send with send_draft after human review, prefer it for consequential mail. It also gives the exact recipe for reply drafts (thread_id, in_reply_to, subject with "Re: ") and points to get_message for the required messageId. This is clear routing guidance.

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