calendar-mcp

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Query free/busy

query_free_busy

Read-onlyIdempotent

Check availability of one or more calendars within a specified time range to identify free or busy periods, without revealing event details.

Instructions

Get busy intervals for one or more calendars, without revealing event details.

Works for other people's calendars addressed by email, which is how you check whether someone is free before proposing a time.

Args: calendar_ids: Calendar IDs or attendee email addresses to check. time_min: Start of the window, ISO 8601 with a UTC offset. time_max: End of the window, ISO 8601 with a UTC offset. account: Account name from 'calendar-mcp accounts'; omit for the default.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`account`	No
`time_max`	Yes
`time_min`	Yes
`calendar_ids`	Yes

Output Schema

TableJSON Schema

Name	Required	Description
`time_max`	Yes	End of the queried window, ISO 8601.
`time_min`	Yes	Start of the queried window, ISO 8601.
`calendars`	No	Per-calendar busy intervals.

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.1.0Sep 7, 2026

TDQS

A4.4/5.0

Behavior4/5

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

Aligned with readOnlyHint and idempotentHint by describing a read-only retrieval, and adds that it omits event details. No contradiction with annotations.

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?

Two concise sentences plus an args list, with no redundant wording or unnecessary detail.

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?

Covers the essential aspects given the annotations and output schema; could mention ordering constraints for time_min/time_max, but this is not critical for invocation.

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

Parameters4/5

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

The description clarifies calendar_ids accepts email addresses and specifies ISO 8601 with UTC offset for time bounds. Response format is not described, but the output schema covers that.

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 the specific verb 'Get' and the resource 'busy intervals for one or more calendars,' and explicitly notes it does not reveal event details, distinguishing it from event-fetching sibling tools.

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

Usage Guidelines4/5

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

Provides a clear use case ('check whether someone is free before proposing a time') and notes that it works with email addresses, but does not explicitly contrast with alternatives like find_events or find_focus_time.

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