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ricleedo

Google Services MCP Server

by ricleedo

calendar-update-event

Modify existing Google Calendar events by updating details like title, time, location, attendees, or description using event ID.

Instructions

Update an existing calendar event

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
eventIdYesEvent ID
calendarIdNoCalendar ID - Available options: 'primary' (Primary Calendar)primary
summaryNoEvent title/summary
descriptionNoEvent description
locationNoEvent location
startDateTimeNoStart date/time in ISO format
endDateTimeNoEnd date/time in ISO format
attendeesNoArray of attendee email addresses

Implementation Reference

  • The main handler function that performs the calendar event update using Google Calendar API. It fetches the existing event, applies updates to provided fields, calls the update API, and returns formatted markdown response.
    export async function updateEvent(
      params: z.infer<ReturnType<typeof updateEventSchema>>
    ) {
      try {
        const auth = createCalendarAuth();
        const calendar = google.calendar({ version: "v3", auth });
    
        // First get the existing event
        const existingEvent = await calendar.events.get({
          calendarId: params.calendarId,
          eventId: params.eventId,
        });
    
        const updatedEvent: any = { ...existingEvent.data };
    
        // Update only the provided fields
        if (params.summary !== undefined) updatedEvent.summary = params.summary;
        if (params.description !== undefined)
          updatedEvent.description = params.description;
        if (params.location !== undefined) updatedEvent.location = params.location;
        if (params.startDateTime !== undefined) {
          updatedEvent.start = {
            ...updatedEvent.start,
            dateTime: params.startDateTime,
          };
        }
        if (params.endDateTime !== undefined) {
          updatedEvent.end = { ...updatedEvent.end, dateTime: params.endDateTime };
        }
        if (params.attendees !== undefined) {
          updatedEvent.attendees = params.attendees.map((email) => ({ email }));
        }
    
        const response = await calendar.events.update({
          calendarId: params.calendarId,
          eventId: params.eventId,
          requestBody: updatedEvent,
          sendUpdates: "all",
        });
    
        const updatedEventData = {
          id: response.data.id,
          summary: response.data.summary,
          start: response.data.start,
          end: response.data.end,
          location: response.data.location,
          description: response.data.description,
          attendees: response.data.attendees,
          htmlLink: response.data.htmlLink,
          updated: response.data.updated,
        };
    
        return {
          content: [
            {
              type: "text" as const,
              text: `# Event Updated Successfully ✅\n\n${formatEventToMarkdown(updatedEventData)}`,
            },
          ],
        };
      } catch (error) {
        return {
          content: [
            {
              type: "text" as const,
              text: `Error updating event: ${
                error instanceof Error ? error.message : String(error)
              }`,
            },
          ],
        };
      }
    }
  • Zod schema defining the input parameters for the updateEvent tool, including eventId, calendarId, and optional fields like summary, description, etc.
    export const updateEventSchema = () =>
      z.object({
        eventId: z.string().describe("Event ID"),
        calendarId: z
          .string()
          .default("primary")
          .describe(getCalendarDescription()),
        summary: z.string().optional().describe("Event title/summary"),
        description: z.string().optional().describe("Event description"),
        location: z.string().optional().describe("Event location"),
        startDateTime: z
          .string()
          .optional()
          .describe("Start date/time in ISO format"),
        endDateTime: z.string().optional().describe("End date/time in ISO format"),
        attendees: z
          .array(z.string())
          .optional()
          .describe("Array of attendee email addresses"),
      });
  • src/index.ts:242-249 (registration)
    Registration of the 'calendar-update-event' tool in the MCP server, linking the name, description, schema, and handler.
    server.tool(
      "calendar-update-event",
      "Update an existing calendar event",
      updateEventSchema().shape,
      async (params) => {
        return await updateEvent(params);
      }
    );
Behavior2/5

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

With no annotations provided, the description carries full burden for behavioral disclosure. 'Update an existing calendar event' implies a mutation operation but doesn't specify required permissions, whether changes are reversible, rate limits, or what happens to unspecified fields. For a write tool with zero annotation coverage, this leaves significant behavioral questions unanswered.

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 a single, efficient sentence that states the core purpose without any wasted words. It's appropriately sized for a tool with comprehensive schema documentation and gets straight to the point.

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?

For a mutation tool with 8 parameters, no annotations, and no output schema, the description is insufficiently complete. It doesn't address behavioral aspects like permissions, side effects, or response format that would help an agent use the tool correctly. The comprehensive schema helps but doesn't compensate for the lack of behavioral context.

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 the schema already documents all 8 parameters thoroughly. The description adds no parameter-specific information beyond what's in the schema. According to scoring rules, with high schema coverage (>80%), the baseline is 3 even with no param info in the description.

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 action ('Update') and resource ('an existing calendar event'), making the purpose immediately understandable. It distinguishes itself from 'calendar-create-event' by specifying 'existing' rather than new events. However, it doesn't explicitly differentiate from 'calendar-get-event' or 'calendar-delete-event' beyond the verb choice.

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 no guidance on when to use this tool versus alternatives like 'calendar-create-event' for new events or 'calendar-delete-event' for removal. It mentions 'existing calendar event' which implies prerequisite knowledge of the event ID, but doesn't state this explicitly or reference sibling tools for context.

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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