Save a draft

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

Annotations indicate this is a mutating operation (readOnlyHint=false) but not destructive. The description adds substantive context beyond annotations: it writes to the Drafts folder, nothing leaves the account, and it is safe when sending is disabled. This gives the agent important behavioral expectations.

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?

Three short sentences with each one earning its place: the core action, the safety rationale, and the crucial condition about EMAIL_ALLOW_SEND. It is front-loaded with the primary purpose and contains no filler.

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?

Given the output schema exists and annotations are present, the description covers the essential context for correct invocation: what the tool does, why it is safe, and when it works. A bit more detail about draft placement or reply_to behavior would be helpful but is not required for basic use.

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 schema already documents every parameter. The description does not add parameter-specific detail, but the baseline of 3 applies because the schema carries the full burden.

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 a specific verb and resource: 'Write a message to the Drafts folder without sending it.' It clearly differentiates from send_email by emphasizing that the user will send it themselves, so an agent can distinguish this tool from its siblings.

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 explains when to use this tool: as the safe way to prepare mail when the user wants to review it first, and it explicitly notes it works when EMAIL_ALLOW_SEND is false. It does not name send_email outright but the contrast is strong enough to guide selection.

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