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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so safety is covered. Beyond that, the description discloses the returned field set and adds a genuinely useful cross-tool behavior note: the attachment_id is the identifier that mail_update_draft removes by. It says nothing about ordering or truncation of results.

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 sentences, front-loaded with the resource scope and then the use case, with no filler. The parenthetical about attachment_id is dense but earns its place by linking to mail_update_draft.

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?

Because there is no output schema, the field enumeration is valuable and largely fills that gap, and annotations cover the read-only safety profile. The remaining hole is pagination/limit behavior and result ordering, which an agent would need to call this reliably.

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?

The single parameter (limit) has 0% schema description coverage and the description never mentions it — no default value, no statement about ordering or what happens when drafts exceed the 1-50 range. With low schema coverage the description was expected to compensate and does not.

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 names a specific resource and scope ('The caller's saved drafts') and enumerates what is returned (recipient, subject, last-touched time, body, attachments), which cleanly separates it from message/thread listing siblings. It never states the verb 'list' explicitly outside the title, but the meaning is unambiguous.

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?

'Use to find a draft to finish, edit or discard' gives a clear triggering context. It does not explicitly exclude alternatives (e.g., use mail_list_messages for non-draft mail), so it stops short of full when/when-not guidance.

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