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AnByoungHyun

Google Calendar MCP

by AnByoungHyun

update_event

Modify Google Calendar event details using an event ID. Update summary, start/end times, description, location, or attendees by passing specific values, ensuring only the provided fields are changed.

Instructions

일정 ID로 일정 정보 수정 (전달된 값만 반영)

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
attendeesNo
descriptionNo
endNo
event_idYes
locationNo
startNo
summaryNo

Implementation Reference

  • The handler function for the 'update_event' tool. It fetches the existing event by ID, updates only the provided fields (summary, start, end, description, location, attendees), and applies the changes using the Google Calendar API patch method.
    @mcp.tool()
    def update_event(
        event_id: str,
        summary: Optional[str] = None,
        start: Optional[str] = None,
        end: Optional[str] = None,
        description: Optional[str] = None,
        location: Optional[str] = None,
        attendees: Optional[List[str]] = None
    ) -> dict[str, Any]:
        """일정 ID로 일정 정보 수정 (전달된 값만 반영)"""
        service = get_calendar_service()
        # 기존 이벤트 조회
        event = service.events().get(calendarId='primary', eventId=event_id).execute()
        # 전달된 값만 업데이트
        if summary is not None:
            event['summary'] = summary
        if description is not None:
            event['description'] = description
        if start is not None:
            event['start'] = {'dateTime': start}
        if end is not None:
            event['end'] = {'dateTime': end}
        if location is not None:
            event['location'] = location
        if attendees is not None:
            event['attendees'] = [{'email': email} for email in attendees]
        # patch로 업데이트
        updated_event = service.events().patch(calendarId='primary', eventId=event_id, body=event).execute()
        return {"message": "일정이 수정되었습니다.", "event": updated_event}
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 discloses a key behavioral trait: '전달된 값만 반영' (only reflects passed values), indicating a partial update rather than full replacement. However, it doesn't cover other important aspects like authentication requirements, error handling, rate limits, or what happens to unchanged fields. The description adds some value but leaves significant gaps for a mutation tool.

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 extremely concise and front-loaded: a single Korean sentence that directly states the tool's purpose and key behavior. Every word earns its place with no redundancy or unnecessary elaboration. The structure is clear and efficient for its content.

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

Completeness2/5

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

Given the complexity (a mutation tool with 7 parameters), lack of annotations, no output schema, and low schema description coverage, the description is incomplete. It covers the basic purpose and partial-update behavior but misses critical context: authentication needs, error cases, response format, and detailed parameter guidance. For an update operation, this leaves too much unspecified for reliable agent use.

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

Parameters2/5

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

The input schema has 7 parameters with 0% description coverage (titles only, no descriptions). The description doesn't add any parameter-specific semantics beyond the general 'only reflects passed values' note. It doesn't explain what each parameter represents (e.g., attendees as an array of strings, start/end as date strings), their formats, or constraints. For a tool with 7 parameters, this is inadequate compensation for the schema gap.

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

Purpose4/5

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

The description clearly states the tool's purpose: '일정 ID로 일정 정보 수정' (update event information by event ID). It specifies the verb (수정/update) and resource (일정 정보/event information), and distinguishes it from siblings like create_event (creation) and get_event_detail (retrieval). However, it doesn't explicitly differentiate from other potential update operations beyond the ID-based approach.

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

Usage Guidelines2/5

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

The description provides minimal guidance: it implies usage when you need to update an existing event using its ID. However, it doesn't specify when to use this versus alternatives (e.g., when to update vs. create a new event with create_event), nor does it mention prerequisites like authentication or permissions. The context is implied but lacks explicit when/when-not instructions.

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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