List Calendars

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

Annotations already declare read-only, idempotent, non-destructive behavior. The description adds valuable behavioral context: names are case-sensitive and vary per user, and the return includes a 'writable' flag, informing the agent about potential permissions. This goes beyond the annotation signals.

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?

Three short sentences plus a return type line. Each sentence adds distinct value: purpose, usage guidance with example, and return format. No filler or repetition of structured fields.

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 zero-parameter, read-only listing tool, the description fully covers purpose, usage timing, case-sensitivity, and return structure. The output schema is simple and explicitly shown. The annotations cover safety, so nothing 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 the baseline is 4 per the rubric. The description correctly omits parameter details since there are none, and the return shape is described, which is useful.

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 clearly states the verb and resource: 'List every calendar configured in macOS Calendar.app.' This is specific and distinguishes it from the sibling mail tools by naming the macOS Calendar.app. It also mentions the exact scope ('every calendar') and purpose.

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?

It explicitly instructs to call this before apple_calendar_create_event to obtain the exact calendar_name, explaining that names are case-sensitive and user-specific. This provides clear when-to-use guidance and rationale, even though no alternative tools are listed (which is fine as no alternatives exist among the siblings).

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