Cal ID MCP Tool Reference

The Cal ID MCP server exposes 58 tools. You rarely need to call them by name — describe what you want and your assistant picks the right one. This reference is for when you’re debugging, checking whether something is possible, or writing a prompt that has to be precise.

Every tool runs the equivalent REST API call as you. Each tool’s own description ends with the route it maps to — for example create_booking reports [POST /booking/] — so you can always trace a tool back to the API reference.

Bookings

Tool	What it does
`get_booking`	List your bookings, with filters for status, attendee, event type, and date ranges
`get_booking_by_id`	Get a single booking by ID
`create_booking`	Create a booking — see Booking through MCP first
`cancel_booking`	Cancel a booking, with options for cancellation scope, seated events, and refunds
`reschedule_booking`	Move a booking to a new time
`change_booking_confirmation_status`	Accept or decline a booking that requires confirmation
`update_booking_reassignbookingautomatically`	Reassign a round-robin booking to the next available host
`update_booking_reassignbookingtouser`	Reassign a round-robin booking to a specific host

Despite the singular name, get_booking lists bookings. Use get_booking_by_id for one specific booking. This mirrors the REST API, where the collection lives at /booking/.

Slots

Tool	What it does
`get_slots`	Get bookable times for an event type or set of users
`create_slots_reserve`	Hold a slot temporarily so nobody else takes it
`get_slot`	Look up a reserved slot by UID
`update_slots`	Update a reserved slot
`delete_slots`	Release a reserved slot

Event types

Tool	What it does
`get_event_types`	List your event types (paginated)
`get_event_types_by_id`	Get one event type by ID
`create_eventtype`	Create an event type
`update_eventtype`	Update an event type
`delete_eventtype`	Delete an event type

Availability and schedules

A schedule is a named set of working hours. An availability is a rule inside one.

Tool	What it does
`get_schedule`	List your schedules
`create_schedule`	Create a schedule
`update_schedule`	Update a schedule
`delete_schedule`	Delete a schedule
`get_availability`	Get your current availability
`create_availability`	Add availability to a schedule
`update_availability`	Update an availability rule
`delete_availability`	Delete an availability rule

Contacts

Tool	What it does
`list_contacts`	List and search contacts, with sorting and pagination
`get_contact`	Get a contact by ID
`create_contact`	Create a contact
`update_contact`	Update a contact
`delete_contact`	Delete a contact
`get_contact_meetings`	Get a contact’s meeting history

Teams

Tool	What it does
`get_teams`	List your teams (paginated)
`get_team`	Get a team by ID
`create_team`	Create a team
`update_team_details`	Update a team’s details
`delete_team`	Delete a team
`get_team_schedules`	Get every team member’s schedule

Team slugs are globally unique across all of Cal ID, not just your account. create_team can fail with a conflict even when you have no teams at all — the slug is simply taken by someone else. Pick a more specific slug and retry.

Team event types

Tool	What it does
`get_team_event_types`	List a team’s event types
`get_team_event_type`	Get one team event type
`create_team_eventtype`	Create a team event type (collective, round-robin, or managed)
`update_team_eventtype`	Update a team event type
`delete_team_eventtype`	Delete a team event type

Team members

Tool	What it does
`get_team_memberships`	List a team’s members
`get_team_membership`	Get one membership
`add_team_member`	Add a member to a team
`update_team_membership`	Update a member’s role or membership
`remove_team_member`	Remove a member from a team

Webhooks

MCP can manage webhook subscriptions. It cannot receive deliveries — those go to your own server. See Build a webhook receiver.

Tool	What it does
`get_webhook`	List your webhooks
`get_webhook_by_id`	Get one webhook by ID
`create_webhook`	Create a webhook subscription
`update_webhook`	Update a webhook
`delete_webhook`	Delete a webhook

Profile

Tool	What it does
`get_users_me`	Get your own profile
`get_users`	Get a user’s public event types by username
`update_user_profile`	Update your profile
`create_users_edit_profile_avatar`	Upload a profile picture

Diagnostics

Tool	What it does
`get_diagnostics_client_ip`	Returns the client IP the server sees

get_diagnostics_client_ip is a temporary internal diagnostic. Don’t build anything on it — it may be removed without notice.

Booking through MCP

This is the single most common failure, and it is not a bug.

You cannot work out bookable times yourself. A time that looks perfectly valid — a weekday, inside your working hours, matching what your booking page shows — can still be rejected with no_available_users_found_error.Always call get_slots first, then book a time it actually returned.

The correct sequence:

Find the event type

Use get_event_types and note the id of the event you want.

Ask for real slots

Call get_slots with that event type ID and a date range. It returns only genuinely bookable times.Pass the ID as a string here — "106371", not 106371.

Book one of them

Pass a time get_slots returned into create_booking as start. Don’t round it, adjust it, or compute your own.Two shape changes catch people between these steps: create_booking wants the same eventTypeId back as a number, and all of its arguments go inside a body object.

{
  "body": {
    "eventTypeId": 106371,
    "start": "2026-08-31T03:45:00.000Z",
    "end": "2026-08-31T04:15:00.000Z",
    "responses": { "name": "Ada Lovelace", "email": "ada@example.com" }
  }
}

The response nests times two levels deeper than you might expect. content[1] holds the usual success/data envelope, and the times sit under data.slots, grouped by date:

{
  "success": true,
  "data": {
    "slots": {
      "2026-08-31": [
        { "time": "2026-08-31T03:45:00.000Z" },
        { "time": "2026-08-31T04:00:00.000Z" }
      ],
      "2026-09-01": [
        { "time": "2026-09-01T03:45:00.000Z" }
      ]
    }
  }
}

The full path to a bookable time is therefore content[1].data.slots["2026-08-31"][0].time. Reading the date keys from the wrong level — straight off content[1], or off a slots key at the top — makes a healthy response look like “no availability.”

The first offered day is often later than you’d assume — minimum booking notice, buffers, and calendar conflicts all push it out. Treat whatever get_slots returns as the truth.

Input gotchas

Worth knowing if you call tools directly rather than prompting conversationally.

Write tools nest everything under a body object

Every tool that sends data — all 25 that create, update, cancel, or reschedule something — takes its fields inside a body object rather than at the top level. (Delete tools send no data, so they have no body.) This is the most common shape error, and the message it produces doesn’t name the field you forgot:

path: ["body"], "Required"

create_booking puts everything in body:

{
  "body": {
    "eventTypeId": 106371,
    "start": "2026-08-31T03:45:00.000Z",
    "end": "2026-08-31T04:15:00.000Z",
    "responses": { "name": "Ada Lovelace", "email": "ada@example.com" }
  }
}

Tools that act on an existing record keep the identifier outside body and the changes inside it. cancel_booking:

{
  "id": 4820193,
  "body": { "cancellationReason": "Rescheduling to next week" }
}

Read-only tools take their parameters flat — get_slots has no body.

eventTypeId is a string for slots and a number for booking

The same ID changes type between the two halves of the booking flow, so the value that just worked fails on the next call.

Tool	Type	Example
`get_slots`	String	`"106371"`
`create_booking`	Number	`106371`

Passing a number to get_slots returns Expected string, received number. Passing a string to create_booking returns Expected number, received string. Neither message tells you which direction to convert, so check the table.get_event_types returns id as a number, which is the form create_booking wants and get_slots doesn’t.These tools also want eventTypeId as a number: create_slots_reserve, update_slots, get_availability, get_team_event_type, update_team_eventtype, and delete_team_eventtype. get_slots is the outlier.

Date parameters are named inconsistently

get_slots takes start and end. So does create_booking, inside its body. reschedule_booking takes only start.startTime and endTime are a different concept entirely — they are the clock times on an availability rule, used by create_availability and update_availability. No booking tool uses them. Sending startTime to create_booking fails as a missing start.

Responses contain two text blocks, not one

Every tool result returns a status line first, then the JSON payload:

content[0] → "HTTP 200 GET /event-types/"
content[1] → { "success": true, "data": [ ... ] }

Parsing content[0] as JSON gets you the status line and fails. Read content[1].

Write tools have no undo

35 of the 58 tools write, and delete_eventtype, delete_team, and cancel_booking take effect immediately. Keep tool-approval prompts enabled in your client so these need a confirmation, or filter them out at the bridge with --ignore-tool — see How access and permissions work.

MCP setup and API details

Connect a client

Setup for Claude, Cursor, ChatGPT, and other MCP clients.

MCP overview

What MCP covers, and how permissions work.

Create a booking

The same slots-then-book flow using the REST API directly.

API reference

Full reference for every endpoint behind these tools.

​Bookings

​Slots

​Event types

​Availability and schedules

​Contacts

​Teams

​Team event types

​Team members

​Webhooks

​Profile

​Diagnostics

​Booking through MCP

​Input gotchas

​MCP setup and API details

Connect a client

MCP overview

Create a booking

API reference

Bookings

Slots

Event types

Availability and schedules

Contacts

Teams

Team event types

Team members

Webhooks

Profile

Diagnostics

Booking through MCP

Input gotchas

MCP setup and API details