mail_prepare_draft

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

Adds real behavioral context beyond the annotations: it returns a preview plus a new operation ID, and the source draft is retained after sending. That non-destructive retention detail is exactly the kind of thing annotations don't convey, though it omits permissions/auth needs and whether repeated calls create duplicate operations.

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, front-loaded with the action, then the return contract, then the post-send state. Every sentence carries distinct information with no padding.

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 no output schema, the description helpfully states the return shape (preview + operation ID). The remaining gap is input identification and prerequisites, but for a moderate-complexity prepare step this is largely complete.

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 0% for all four required parameters, and the description never mentions them. It alludes to 'the source draft' but never explains that accountId/folder/uid/uidValidity identify which draft to prepare, so the burden of explaining the inputs is entirely unmet.

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?

States a specific verb+resource ('Prepare a server draft for sending') and explicitly separates the action from sending, which distinguishes it from mail_send_prepared. It does not, however, name sibling tools like mail_prepare or mail_update_draft, so the boundary against those is left to inference.

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?

'sending is separate' implies the two-step flow (prepare here, then mail_send_prepared), which is useful routing. But there is no explicit when-to-use/when-not statement, no prerequisites (does the draft already have to exist?), and no comparison to mail_prepare or mail_save_draft.

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