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

Despite annotations already marking this as read-only and non-destructive, the description adds substantial behavioral context: it explains access modes, default/owned/shared status, hidden calendars, time zone limitations, and what happens with unread accounts and cutShort results. It also discloses the reconnection workflow, which is important operational behavior.

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?

The description is dense and run-on, packing many output-field caveats into two long sentences without paragraphing or list formatting. The details are useful given the lack of an output schema, but the structure is not concise or easy to scan.

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 no output schema and no parameters, the description carries the full burden of explaining return values and edge cases. It does so thoroughly, covering account/provider naming, ownership, access, time zones, busyShownIn, unread accounts, cutShort, and reconnectAt.

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 no parameter semantics to explain. The baseline score of 4 applies because the schema is empty and does not need description-level compensation.

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 opens with a specific verb and resource: 'List every calendar of every connected Outlook.com, Microsoft 365, Google, iCloud and calendar server account.' It clearly scopes the operation to calendars rather than events, making it distinguishable from siblings such as events_list and circles_list.

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?

Usage is implied by the listing operation and the detailed account/calendar context, but there is no explicit guidance on when to call this versus events_list, free_times_find, or other siblings. No exclusions or prerequisites are stated.

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