> ## Documentation Index > Fetch the complete documentation index at: https://developer.mailbeast.ai/llms.txt > Use this file to discover all available pages before exploring further. # Start campaign > Begin sending (or resume a paused campaign). Needs a lead list and a sequence - returns 400 if the campaign has nothing to send. Requires one of the following scopes: `campaigns:lifecycle`, `campaigns:all`, `all:all`. ## OpenAPI ````yaml /openapi.json post /v1/campaigns/{id}/start openapi: 3.0.0 info: title: MailBeast Public API description: >- Task-shaped REST API for campaigns, leads, deliverability, verification and lead discovery. Authenticate with an API key (`Authorization: Bearer mb_live_…`); the workspace is resolved from the key. version: '1' contact: {} servers: - url: https://api.mailbeast.ai security: [] tags: - name: API Keys description: Create, list and revoke API keys programmatically. - name: Campaigns description: Create, configure, launch and monitor email campaigns. - name: Leads description: Add, read, update and bulk-manage a campaign’s leads. - name: Workspace description: Read usage, subscription and workspace identity. - name: Email Accounts description: >- Connect and manage the sending mailboxes your campaigns send from (SMTP/IMAP or native OAuth). - name: Analytics description: Engagement reporting – per campaign, over time, and across the workspace. - name: Lead Finder description: >- Discover new companies and leads. List past searches and poll a running search’s progress. paths: /v1/campaigns/{id}/start: post: tags: - Campaigns summary: Start campaign description: >- Begin sending (or resume a paused campaign). Needs a lead list and a sequence - returns 400 if the campaign has nothing to send. Requires one of the following scopes: `campaigns:lifecycle`, `campaigns:all`, `all:all`. operationId: campaigns_start parameters: - name: id required: true in: path schema: type: string format: uuid example: a7d4e2f1-08b3-4c65-9e7a-1b2c3d4e5f60 - name: Idempotency-Key in: header description: >- Optional. A unique key you generate (max 255 chars, such as a UUID) that makes this request safe to retry. Retrying with the same key replays the original response instead of repeating the operation. Reusing a key with a different body returns `422`. required: false schema: type: string maxLength: 255 example: a1b2c3d4-e5f6-7890-abcd-ef1234567890 responses: '200': description: '' content: application/json: schema: $ref: '#/components/schemas/CampaignLifecycleApiResponseDto' '400': description: The request body or parameters failed validation. content: application/json: schema: $ref: '#/components/schemas/ApiErrorDto' example: error: type: invalid_request_error code: validation_failed message: One or more fields are invalid. status: 400 requestId: e4f1c0b2-6a3d-4b8e-9f21-0a1b2c3d4e5f details: - name should not be empty '401': description: Missing or invalid API key. content: application/json: schema: $ref: '#/components/schemas/ApiErrorDto' example: error: type: authentication_error code: unauthenticated message: Missing or invalid API key. status: 401 requestId: e4f1c0b2-6a3d-4b8e-9f21-0a1b2c3d4e5f '403': description: >- The key lacks a required scope, or the plan does not include API access. content: application/json: schema: $ref: '#/components/schemas/ApiErrorDto' example: error: type: authorization_error code: permission_denied message: This API key is missing the required scope. status: 403 requestId: e4f1c0b2-6a3d-4b8e-9f21-0a1b2c3d4e5f '404': description: The resource does not exist in your workspace. content: application/json: schema: $ref: '#/components/schemas/ApiErrorDto' example: error: type: invalid_request_error code: not_found message: Resource not found. status: 404 requestId: e4f1c0b2-6a3d-4b8e-9f21-0a1b2c3d4e5f '409': description: >- The request conflicts with current state - e.g. a request with the same Idempotency-Key is still being processed, or the operation partially applied. content: application/json: schema: $ref: '#/components/schemas/ApiErrorDto' example: error: type: invalid_request_error code: conflict message: The request conflicts with an existing resource. status: 409 requestId: e4f1c0b2-6a3d-4b8e-9f21-0a1b2c3d4e5f '422': description: >- The Idempotency-Key was already used with a different request body. Use a new key for a new operation. content: application/json: schema: $ref: '#/components/schemas/ApiErrorDto' example: error: type: invalid_request_error code: idempotency_key_reused message: >- The Idempotency-Key was already used with a different request body. Use a new key for a new operation. status: 422 requestId: e4f1c0b2-6a3d-4b8e-9f21-0a1b2c3d4e5f '429': description: >- Rate limit exceeded - retry after the interval in the Retry-After header. content: application/json: schema: $ref: '#/components/schemas/ApiErrorDto' example: error: type: rate_limit_error code: rate_limited message: >- Too many requests. Retry after the interval in the Retry-After header. status: 429 requestId: e4f1c0b2-6a3d-4b8e-9f21-0a1b2c3d4e5f retryAfter: 30 security: - ApiKey: [] components: schemas: CampaignLifecycleApiResponseDto: type: object properties: id: type: string format: uuid example: a7d4e2f1-08b3-4c65-9e7a-1b2c3d4e5f60 status: type: string enum: - draft - scheduled - active - paused - stopped - completed - failed example: paused success: type: boolean example: true required: - id - status - success ApiErrorDto: type: object properties: error: $ref: '#/components/schemas/ApiErrorBodyDto' required: - error ApiErrorBodyDto: type: object properties: type: type: string example: authorization_error description: Broad error class. code: type: string example: permission_denied description: Stable machine-readable code to switch on. message: type: string example: This API key is missing the required scope. status: type: number example: 403 requestId: type: string example: e4f1c0b2-6a3d-4b8e-9f21-0a1b2c3d4e5f description: Correlation id - quote it in support requests. details: description: Field-level validation messages (present on validation errors). example: - name should not be empty type: array items: type: string retryAfter: type: number description: Seconds to wait before retrying (present on 429 responses). example: 30 required: - type - code - message - status - requestId securitySchemes: ApiKey: scheme: bearer bearerFormat: mb_live_… type: http ```` ## Related topics - [Campaigns](/campaigns.md) - [Create a campaign](/api-reference/campaigns/create-a-campaign.md) - [Authentication](/authentication.md) - [Update a campaign](/api-reference/campaigns/update-a-campaign.md) - [Campaign analytics over time](/api-reference/analytics/campaign-analytics-over-time.md)