create_reply_draft

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

Annotations already declare readOnlyHint=false, destructiveHint=false, and openWorldHint=true, and the description is consistent with them ('Nothing is sent' matches a non-destructive draft creation). Beyond that, it adds genuinely useful behavioral limits: recipients/Re: subject/threading are inherited from the original, the reply cannot be re-addressed, and it cannot carry attachments.

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-loaded with the action and outcome, then the constraints. No filler or restated schema noise; every clause carries information.

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 5 parameters fully documented in the schema, annotations covering the safety profile, and no output schema to explain, the description is nearly complete for correct invocation. It omits minor operational detail such as which folder the new draft lands in, but nothing essential to calling it correctly is missing.

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 100%, so the baseline is 3, but the description adds real meaning beyond the schema by explaining that recipient, subject, and threading parameters deliberately do not exist because they come from the original. The 'written above the quoted original' note also contextualizes the includeQuote toggle.

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+resource ('Save a reply to an email as a draft') and clarifies the outcome ('for the user to review and send'), so the agent knows exactly what is produced. It does not explicitly distinguish itself from the sibling update_draft (which edits an existing draft), leaving that inference to the agent.

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?

'Save a reply ... as a draft for the user to review and send' plus 'Nothing is sent' gives clear situational context for when this tool applies. However, it names no alternatives or exclusions (e.g., use update_draft to modify an existing draft), so routing between siblings still requires inference.

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