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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds genuine value with the result ordering (pending first) and the meaning of lastError on failures, but it says nothing about result volume, limits, or empty states.

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 with no filler. The ordering rule is front-loaded and the diagnostic note follows where it is most useful.

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?

A read-only single-parameter list tool with an output schema and full annotation coverage needs little more than this. The ordering and failure semantics are the only behaviors the structured fields cannot express, and both are present; only result-size expectations are 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% for the single accountId parameter, and the schema itself explains that it is optional when exactly one account is connected. The description adds nothing about the parameter, which is acceptable at this coverage level but not additive.

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 ("List scheduled sends") and immediately characterizes the content: pending first, then sent/failed/canceled. This clearly separates it from list_emails or get_email, though it never names a sibling explicitly.

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?

Usage is implied by the resource name rather than stated. There is no explicit when-to-use guidance, no mention of how this relates to cancel_scheduled_email or preview_send, and no note about when to supply accountId.

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