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

Annotations already cover the safety profile (readOnlyHint=true, destructiveHint=false, openWorldHint=false), so the bar is lower, yet the description still adds substantial behavior: it discloses ownership vs. mere sharing, Google-specific access modes (edit/read/freeBusy), hidden calendars, per-calendar time zones only where the provider keeps them, the busyShownIn cross-account view, and the unread/cutShort failure and truncation cases. This is genuinely useful context beyond the annotations, though it documents the response rather than any call-time 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?

It is front-loaded with the operation and every clause carries return-field information rather than padding, but the entire description is a single sprawling run-on sentence built from comma-separated clauses and em-dash asides. It front-loads well but is hard to parse and would benefit from being broken into structured sentences.

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 what comes back, and it does so in detail, including the unread (unreadable accounts / restricted events) and cutShort (more calendars than one answer carries) edge cases. The main omission is any explicit statement of how to page past the described cutShort truncation.

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 and the schema is empty with additionalProperties=false, so there are no parameter semantics to explain; the baseline for a 0-parameter tool is 4. Nothing in the description conflicts with the schema.

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 and Google account') and scopes the breadth across all accounts, which cleanly separates it from siblings like events_list or free_times_find. An agent can identify the operation and its scope without opening the schema.

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 only implied: the tool lists calendars, so an agent infers it should be called for calendar discovery, but no alternative is named and no precondition or 'use this instead of X' guidance is given. Given the 0-parameter, list-everything nature of the tool the implied usage is fairly unambiguous, but it stops short of explicit routing.

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