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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the safety profile is covered. The description adds a genuinely new behavioral fact — pending drafts expire after 24 hours — which affects urgency and result interpretation, though it doesn't discuss ordering or empty-result behavior.

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?

One core sentence with the purpose and returned fields front-loaded, plus a short second sentence carrying the expiry constraint. No filler, no restating of the title.

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 zero parameters, no output schema, and annotations covering the safety profile, the description supplies the remaining essentials: what comes back (recipient, topic, age), why to call it, and the 24-hour expiry. Nothing an agent needs in order to call 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?

The tool takes zero parameters, so there is nothing for the description to disambiguate; the schema coverage baseline applies. The description's field enumeration is return-value context rather than parameter guidance, which is appropriate here.

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 and resource (list pending/unsent drafts) and enumerates the returned fields (recipient, topic, age), which distinguishes it immediately from siblings like cancel_draft or get_thread.

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?

Gives two concrete use cases — recovering a draft whose id was lost, or cleaning up before calling cancel_draft — so the agent knows why to call it and what pairs with it. It stops short of an explicit 'do not use this when...' exclusion, which keeps it from a 5.

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