List Calendars

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

Annotations already declare readOnly, idempotent, and non-destructive, so the safety bar is low; the description still adds real value by disclosing the required calendar.read scope and the cursor-based pagination loop. It stops short of describing ordering or what a calendar record contains, though the output schema covers returns.

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, action first, then the permission precondition, then the pagination tactic. No filler; the only mild ambiguity is "selected mailbox," which is not tied explicitly to mailbox_id.

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 list tool with full schema coverage and an output schema needs only purpose, scope, and paging guidance, all of which are present. Minor gap: it does not clarify how the "selected mailbox" is determined when mailbox_id is omitted and multiple mailboxes are granted.

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 schema already documents all three parameters at 100% coverage, including limit bounds, cursor format, and the mailbox_id omission rule. The description's "small limit" and "continue with the returned cursor" restate schema semantics without adding new meaning, so baseline 3 applies.

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 calendars") scoped to a mailbox, which distinguishes it from the closely named sibling mailbox_list_calendar_events by resource type rather than by explicit callout. An agent can infer the difference, but the description never names the alternative outright.

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 procedural guidance (use a small limit, continue with the returned cursor) and a permission prerequisite (calendar.read), plus "selected mailbox" hints at mailbox targeting. It does not state when to prefer this over mailbox_list_calendar_events or mailbox_get_calendar, so usage is implied rather than fully directed.

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