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m365_calendar_availability

Read-onlyIdempotent

Check free/busy schedules for specified users and a time range, including 30-minute availability, to find meeting slots without booking or sending invitations.

Instructions

Read free/busy schedules for the supplied users and time range, including a 30-minute availability view. This does not book a meeting or send invitations. Use m365_calendar_create after selecting a time, or m365_calendar_list for your event details. Returns per-user schedules and any Graph-reported errors.

Input Schema

NameRequiredDescriptionDefault
usersYesComma-separated mailbox email addresses to check
endDateTimeYesRange end (ISO 8601), using the same timezone conventions as startDateTime
startDateTimeYesRange start (ISO 8601); no offset uses the configured timezone; Z/an offset specifies an instant

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed3 schema fields changedv1.2.1
    • changedInput schema / properties / endDateTime / description
      Previous value: -"End (ISO 8601)"New value: +"Range end (ISO 8601), using the same timezone conventions as startDateTime"
    • changedInput schema / properties / startDateTime / description
      Previous value: -"Start (ISO 8601)"New value: +"Range start (ISO 8601); no offset uses the configured timezone; Z/an offset specifies an instant"
    • changedInput schema / properties / users / description
      Previous value: -"User emails to check, comma-separated"New value: +"Comma-separated mailbox email addresses to check"
  2. First observedv1.0.7

TDQS

A4.4/5.0
Behavior4/5

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

Annotations already cover readOnly/idempotent/non-destructive, and the description adds real value beyond them: it clarifies the operation is non-committal (no booking, no invitations) and that per-user schedules plus Graph-reported errors are returned. It does not mention permission requirements for reading other users' free/busy, which is the main remaining gap.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Three short sentences, front-loaded with the core action, then the negative boundary, then sibling routing. Every sentence carries distinct information with no repetition of the name or schema.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With no output schema, the description steps in to say what is returned (per-user schedules and Graph errors), and it rules out side effects. It stops short of noting practical constraints such as permission scope for other mailboxes or Graph limits on users/ranges, which would matter for a free/busy lookup.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so all three parameters (users, startDateTime, endDateTime) are already documented, including timezone handling. The description only restates 'supplied users and time range' and adds the 30-minute view granularity, which is output detail rather than parameter meaning. Baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource: 'Read free/busy schedules for the supplied users and time range', plus the granularity of the result ('30-minute availability view'). It is clearly distinguishable from m365_calendar_list (event details) and m365_calendar_create (booking), both of which it names.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives an explicit negative boundary ('does not book a meeting or send invitations') and names the follow-up alternative with its condition: use m365_calendar_create after selecting a time, m365_calendar_list for event details. An agent knows exactly when to pick this tool versus its siblings.

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