google-calendar-mcp

get_freebusy

Retrieve free/busy information for a specified time range across multiple calendars to identify available slots.

Instructions

指定した期間の空き時間情報を取得します。複数のカレンダーの予定が埋まっている時間帯を確認できます

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "timeMin": "<timeMin>",
      "timeMax": "<timeMax>"
    },
    "name": "get_freebusy"
  }
}

Input Schema

Name	Required	Description
`timeMax`	Yes	確認終了日時（ISO 8601形式）
`timeMin`	Yes	確認開始日時（ISO 8601形式）
`timeZone`	No	タイムゾーン（例: Asia/Tokyo）
`calendarIds`	No	確認するカレンダーIDのリスト

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.0.0Aug 9, 2026

TDQS

A3.8/5.0

Behavior3/5

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

No annotations are provided, so the description carries the full burden. It conveys that this is a read operation retrieving availability for a period and multiple calendars, but it does not disclose the response format, limitations, or that it returns busy/free markers rather than event details. This is a minimal but acceptable level of transparency.

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?

The description is exceptionally concise, consisting of two sentences that front-load the primary purpose and add the multi-calendar detail. No unnecessary words or repetition.

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?

Given the full schema coverage and the simple nature of a free/busy query, the description provides the essential context. However, since there is no output schema, it could have described the return structure more explicitly, but the mention of free and occupied time slots is mostly sufficient.

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?

The schema provides 100% coverage for all four parameters, so the baseline of 3 applies. The description adds no parameter-specific syntax or details beyond what the schema already offers, only loosely aligning 'specified period' with timeMin/timeMax and 'multiple calendars' with calendarIds.

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?

The description explicitly states the function: retrieving free/busy information for a specified period. It also mentions the ability to check time slots where multiple calendars are occupied, which clearly distinguishes it from sibling tools like list_events or search_events.

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

Usage Guidelines3/5

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

The description implies its use case (checking availability across calendars) but provides no explicit guidance on when to use it versus alternatives, nor any exclusions. It could be improved by contrasting with list_events or search_events.

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

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