---
title: Repository Contract
description: Connect WebMCP calendar tools to your existing API or database with list, get, create, update, and delete.
---

WebMCP calendar tools call an object you provide — [`CalendarEventRepository`](/integrations/fullcalendar/reference/calendar-event-repository) with five methods that wrap your existing API or database.

Pass it as the `events` option to [`useFullCalendarWebMCP`](/integrations/fullcalendar/reference/use-fullcalendar-webmcp).

Authorization and authentication are host-owned. The repository must enforce the same rules for agent and UI traffic. See [Security](/integrations/fullcalendar/concepts/security).

## One source of truth

FullCalendar WebMCP does not store events. Human UI edits and agent tool calls both go through your repository. After an agent mutation, `onEventsChanged` refreshes the UI from that same source.

```text
Human (FullCalendar UI) ──┐
                          ├──→ your persistence ──→ onEventsChanged ──→ FullCalendar
Agent (WebMCP tools) ─────┘
```

Reject a repository promise and the tool fails — no second copy of events to drift out of sync.

## Methods

| Method | Purpose |
|---|---|
| `list` | Return events, optionally filtered by range or title text |
| `get` | Return one event by id, or `null` |
| `create` | Persist a new event and return it with its id |
| `update` | Apply changes and return the updated event |
| `delete` | Remove an event by id |

```ts
export interface CalendarEventRepository {
  list(
    query?: CalendarEventQuery,
    options?: { signal?: AbortSignal },
  ): Promise<CalendarEvent[]>;

  get(
    id: string,
    options?: { signal?: AbortSignal },
  ): Promise<CalendarEvent | null>;

  create(
    input: CreateCalendarEventInput,
    options?: { signal?: AbortSignal },
  ): Promise<CalendarEvent>;

  update(
    id: string,
    input: UpdateCalendarEventInput,
    options?: { signal?: AbortSignal },
  ): Promise<CalendarEvent>;

  delete(
    id: string,
    options?: { signal?: AbortSignal },
  ): Promise<void>;
}
```

## Filters on `list`

```ts
export interface CalendarEventQuery {
  start?: string; // inclusive ISO 8601
  end?: string;   // exclusive ISO 8601
  text?: string;  // case-insensitive title substring
}
```

## Cancellation

Every method accepts an optional `{ signal?: AbortSignal }`. Forward it to `fetch` when you want aborted agent calls to cancel in-flight requests.

## Any backend

REST, Server Actions, Supabase, Prisma, GraphQL, or an in-memory store for prototypes all work — as long as the same operations serve humans and agents.

For domain mapping and optional metadata, see [Custom event models](/integrations/fullcalendar/guides/custom-event-model).