Update a draft

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

The description discloses critical behavioral traits beyond the annotations: omitted fields are dropped, the draft id remains stable, the underlying message id changes, and the response is the updated draft. The destructiveHint is consistent and the description enriches it by explaining exactly what gets replaced and what side effect occurs.

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?

Four sentences, each carrying distinct information: the replacement semantics, the prerequisite, the state behavior, and the return value. The 'REPLACES' warning is front-loaded, and there is no filler or redundant restating of the schema.

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 10-parameter tool with no output schema, the description is largely complete: it covers prerequisites, full-replacement semantics, reply-draft specifics, id stability, and the return value. It doesn't enumerate every parameter but the schema already does that. A brief note on error conditions or permissions would make it fully complete, but that's a minor gap.

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%, so the baseline is 3. The description adds semantic value by explaining that parameters represent the complete new state rather than deltas, and calls out the thread_id/in_reply_to pairing for reply drafts. This goes beyond simple parameter descriptions and prevents common misuse.

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 opens with 'REPLACES a draft's entire message', naming the specific verb and resource, and immediately clarifies the key distinguishing trait: this is not a partial edit. It clearly differentiates update_draft from siblings like create_draft and delete_draft by focusing on replacement of an existing draft's full content.

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 explicit procedural guidance: read current content with get_draft first, then pass the complete new state. It also states when thread_id/in_reply_to are relevant. It doesn't explicitly contrast with alternatives like create_draft or send_draft, but the get_draft prerequisite and full-replacement instruction provide clear usage context.

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