calendar_calendars

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

With no annotations, the description carries the burden and does disclose useful behavior: it is a read-only enumeration on the device, `primary` identifies the account's own calendar and is the implicit target of calendar.create, and hidden-but-synced calendars still appear. It stops short of stating ordering, completeness guarantees, or how many calendars are returned.

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 lines, front-loaded with what is listed and its fields, then the follow-on usage note. No filler and no repetition of schema content.

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?

No output schema exists, so the description compensates by enumerating the returned fields (id, name, account, colour, access level, visible, sync). Combined with the follow-on guidance for the `calendar` parameter, an agent has everything needed to call it and use the result.

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%, so visible_only and writable_only are already fully documented at the parameter level, setting the baseline at 3. The description adds conceptual context (visible vs sync, the meaning of `primary`) but never refers to the filter parameters by name.

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 the calendars on the phone") and enumerates the fields returned, so an agent can distinguish it from calendar_events, calendar_get, or calendar_set_calendar immediately. The parenthetical field list makes the resource concrete rather than generic.

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?

Explicitly tells the agent how to use the output: feed `id` (or name) into the `calendar` parameter of other calendar ops, and notes `primary` is the default target of calendar.create. It does not, however, say when not to use it (e.g. vs calendar_get or calendar_set_calendar), so routing against siblings is only implied.

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