list_calendars

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

No annotations are provided, so the description carries the burden, but 'List' strongly implies a non-mutating read and the tool takes no parameters. The description does disclose that only names are returned, which sets expectations about minimal output. It says nothing about ordering, empty results, or permissions, which leaves gaps for a no-annotation tool.

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?

A single front-loaded sentence with zero filler. The key constraint (names only, event-capable calendars) is stated immediately.

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 an output schema present, the return shape needn't be described, and a zero-parameter read tool needs little more than this. The only omission is any pointer to list_calendar_details for richer per-calendar data, which would help an agent choose between the two.

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 has zero parameters, so there is nothing for the description to disambiguate; baseline 4 applies. The phrase 'that can hold events' is effectively a filter semantic applied by the tool, which is mildly informative.

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 (List) and resource (iCloud calendars), plus a meaningful scope qualifier: only calendars 'that can hold events'. This implicitly separates it from list_calendar_details, but it doesn't name that sibling or state the distinction explicitly, so it falls short of 5.

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?

The 'can hold events' qualifier implies this is a discovery step before creating or moving an event, but there is no explicit when-to-use, when-not-to-use, or alternative named (e.g., list_calendar_details for richer metadata). Usage is only inferred.

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