update_draft

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

Beyond the annotations, the description explains that this is a partial update: only passed fields change, the answering thread and existing attachments are preserved, and the message remains unsent. It does not mention the keep_attachments=false exception, but that detail is covered by the schema.

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 three tight sentences, front-loaded with the core action and followed by the most relevant behavioral constraints. There is no redundant or filler wording.

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 mutation tool with eight parameters and no output schema, the description covers purpose, partial-update behavior, preservation of thread and attachments, and the fact that the draft is not sent. The remaining details are reasonably handled by the schema, though the keep_attachments exception could have been surfaced.

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 50%, with account, draft_id, attachments, and keep_attachments documented in the schema while to, cc, body, and subject rely on obvious names. The description adds important partial-update semantics but does not explain parameter-specific behavior such as dropping attachments.

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 verb and resource: 'Edits an existing draft'. It also explicitly distinguishes this from creating a new draft, which directly separates it from the sibling create_draft tool.

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?

It gives clear usage context by saying this edits an existing draft instead of creating a new one, and clarifies that the draft is not sent. It does not name create_draft or list_drafts explicitly, but the alternative behavior is clear.

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