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

With no annotations provided, the description carries the full burden. It discloses that calendars outside the user's access are not returned, which is a useful behavioral trait. However, it does not explicitly state that this is a read-only operation, nor does it mention authentication requirements or rate limits. The access restriction is the key behavior, and it is covered, but richer context would be beneficial.

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 two sentences, with the primary purpose stated first and the usage guidance immediately following. It is front-loaded and efficient, with no redundant phrases or filler. Every sentence adds value, making it highly concise and well-structured.

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?

Given the tool's simplicity (one parameter, no output schema), the description covers the essential context: what it does, how the result is used (to get calendarId), and a scope limitation (access filtering). It does not describe the return format in detail, but that is not critical for a listing tool. Overall, it is sufficiently complete for an agent to understand when and how to use it.

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 description for the mailbox parameter is already quite detailed: it specifies the email address format and instructs to call list_authorized_mailboxes for options. The tool description adds no further parameter information, but since schema coverage is 100%, the baseline of 3 is appropriate. The description does not need to repeat what the schema already explains.

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 'List' and the resource 'calendars on one Outlook/Microsoft 365 account'. It distinguishes itself from sibling tools like list_google_calendars and list_outlook_calendar_events by specifying the account scope and the fact it returns calendars, not events. The mention of 'Start here' further clarifies its role as the entry point for calendar-related operations.

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?

The description explicitly says 'Start here to get the calendarId the event tools take' and explains that omitting the calendarId makes event tools use the default calendar. This tells the agent when to invoke this tool. It also notes that only accessible calendars are returned, which clarifies the result scope. However, it does not explicitly contrast with list_google_calendars or other alternatives, so it loses one point.

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