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

Annotations only declare the generic non-read-only, non-destructive profile; the description adds real behavioral detail beyond that — account placement (same account as the default list, usually iCloud), the case-insensitive duplicate failure mode, the two-phase preview/confirm flow, and the returned id. These are exactly the traits an agent needs and none are recoverable from the annotations.

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?

Four compact sentences, front-loaded with purpose and account scope, then failure mode, then the confirm protocol, then routing. Every sentence carries information, though the final routing sentence could arguably live in the sibling's description instead.

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?

For a two-parameter, non-destructive creation tool with an output schema, nothing material is missing: scope, failure conditions, the confirm protocol, and the returned id are all covered, and return-value detail need not be expanded since an output schema exists.

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 coverage is 100%, so the baseline is 3, but the description genuinely enriches both parameters: it explains that omitting confirm yields a preview rather than a creation, and that name is subject to a case-insensitive uniqueness check. That is meaning beyond the terse schema text 'Must be true to create'.

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 ('Creates a new list in Apple Reminders'), pins the target account, and distinguishes itself from the reminder-creating sibling by routing the agent to create_reminder for the follow-up step. An agent can tell this apart from create_reminder, rename_reminder_folder, and delete_reminder_folder without opening any schema.

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 clear operating context: it fails on duplicate names (case-insensitive), and it explains the preview-vs-create gate. It also names the follow-up tool (create_reminder) for populating the list. What it lacks is guidance on the list-creation alternative path or when a preview call is preferable, so it stops short of full when/when-not coverage.

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