Prelude Transactional Messaging API

openapi: 3.0.3
info:
  title: Prelude API
  description: >-
    Prelude is a phone and email verification, transactional messaging, phone
    number intelligence (lookup), and anti-fraud API - "the trust layer between
    your signups and your business." This document models Prelude's public REST
    API v2 (base https://api.prelude.dev/v2) across four products: Verify
    (create / check one-time passcodes over SMS, WhatsApp, RCS, Viber, and
    voice), Notify (transactional messaging), Lookup / Intel (phone number
    intelligence - line type, carrier, ported / temporary flags, CNAM), and
    Watch (anti-fraud risk prediction and feedback). All requests authenticate
    with a Bearer API key (Authorization: Bearer YOUR_API_KEY) obtained from the
    Prelude dashboard under All Services > Configure > Keys. Endpoint paths and
    request / response schemas are grounded in the live Prelude documentation at
    docs.prelude.so as of 2026-07-11; the Watch events (dispatch-events) endpoint
    is modeled from documentation references and marked accordingly.
  version: '2.0'
  contact:
    name: Prelude
    url: https://prelude.so
servers:
  - url: https://api.prelude.dev/v2
    description: Prelude API v2
security:
  - bearerAuth: []
tags:
  - name: Verification
    description: Create and check one-time passcode (OTP) verifications.
  - name: Transactional
    description: Send transactional messages over SMS, RCS, and WhatsApp.
  - name: Lookup
    description: Phone number intelligence - line type, carrier, and flags.
  - name: Watch
    description: Anti-fraud risk prediction and outcome feedback.
paths:
  /verification:
    post:
      operationId: createVerification
      tags:
        - Verification
      summary: Create or retry a verification
      description: >-
        Creates a new verification for a phone number or email address and
        dispatches a one-time passcode. If a non-expired verification already
        exists for the same target within the verification window, this endpoint
        performs a retry instead of creating a new verification.
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/CreateVerificationRequest'
      responses:
        '200':
          description: The created or retried verification.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Verification'
        '400':
          $ref: '#/components/responses/BadRequest'
        '401':
          $ref: '#/components/responses/Unauthorized'
        '429':
          $ref: '#/components/responses/RateLimited'
  /verification/check:
    post:
      operationId: checkVerification
      tags:
        - Verification
      summary: Check a code
      description: >-
        Validates a one-time passcode submitted by an end user against an active
        verification for the given target.
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/CheckVerificationRequest'
      responses:
        '200':
          description: The verification check result.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/VerificationCheck'
        '400':
          $ref: '#/components/responses/BadRequest'
        '401':
          $ref: '#/components/responses/Unauthorized'
        '429':
          $ref: '#/components/responses/RateLimited'
  /lookup/{phone_number}:
    get:
      operationId: lookupPhoneNumber
      tags:
        - Lookup
      summary: Look up a phone number
      description: >-
        Returns intelligence about a phone number - line type, current and
        original carrier (network) info, ported / temporary flags, and
        optionally the caller name (CNAM). Useful for number validation and
        anti-fraud enrichment.
      parameters:
        - name: phone_number
          in: path
          required: true
          description: An E.164 formatted phone number to look up.
          schema:
            type: string
            example: '+30123456789'
        - name: type
          in: query
          required: false
          description: >-
            Optional lookup features to include. Currently supports `cnam` to
            retrieve the caller ID name (requires enablement on your account).
          schema:
            type: array
            items:
              type: string
              enum:
                - cnam
      responses:
        '200':
          description: Phone number intelligence.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/LookupResponse'
        '400':
          $ref: '#/components/responses/BadRequest'
        '401':
          $ref: '#/components/responses/Unauthorized'
  /watch/predict:
    post:
      operationId: predictWatch
      tags:
        - Watch
      summary: Predict signup risk
      description: >-
        Scores a signup identifier (phone number or email address) as
        `legitimate` or `suspicious`, optionally using anti-fraud signals such
        as IP, device id, and device platform, plus a frontend SDK dispatch id.
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/PredictWatchRequest'
      responses:
        '200':
          description: The risk prediction.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/PredictWatchResponse'
        '400':
          $ref: '#/components/responses/BadRequest'
        '401':
          $ref: '#/components/responses/Unauthorized'
  /watch/feedback:
    post:
      operationId: sendWatchFeedback
      tags:
        - Watch
      summary: Send feedbacks about verifications
      description: >-
        Reports what actually happened in your verification flow (for example a
        verification started or completed) so Watch can update its counters and
        improve future predictions. Accepts up to 100 feedback items per request.
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/FeedbackWatchRequest'
      responses:
        '200':
          description: Feedback acknowledgement.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/FeedbackWatchResponse'
        '400':
          $ref: '#/components/responses/BadRequest'
        '401':
          $ref: '#/components/responses/Unauthorized'
  /watch/dispatch-events:
    post:
      operationId: dispatchWatchEvents
      tags:
        - Watch
      summary: Dispatch events
      description: >-
        Sends frontend interaction events (associated with a dispatch id from
        the Prelude frontend SDK) to Watch to enrich risk scoring. NOTE - this
        endpoint is referenced in the Prelude documentation but its full request
        / response schema was not published at review time; the request shape
        below is modeled and unconfirmed.
      x-modeled: true
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/DispatchEventsRequest'
      responses:
        '200':
          description: Events acknowledgement.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/FeedbackWatchResponse'
        '401':
          $ref: '#/components/responses/Unauthorized'
  /notify:
    post:
      operationId: sendTransactionalMessage
      tags:
        - Transactional
      summary: Send a transactional message
      description: >-
        Sends a template-based transactional message to a recipient over the
        best available channel (SMS, RCS, or WhatsApp). Templates are configured
        with your Prelude Customer Success team.
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/SendMessageRequest'
      responses:
        '200':
          description: The created message.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Message'
        '400':
          $ref: '#/components/responses/BadRequest'
        '401':
          $ref: '#/components/responses/Unauthorized'
components:
  securitySchemes:
    bearerAuth:
      type: http
      scheme: bearer
      description: >-
        Bearer API key passed as `Authorization: Bearer YOUR_API_KEY`. Obtain
        keys from the Prelude dashboard under All Services > Configure > Keys.
  responses:
    BadRequest:
      description: The request was invalid.
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
    Unauthorized:
      description: Missing or invalid API key.
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
    RateLimited:
      description: Too many requests.
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
  schemas:
    Target:
      type: object
      required:
        - type
        - value
      properties:
        type:
          type: string
          description: The kind of target identifier.
          enum:
            - phone_number
            - email_address
        value:
          type: string
          description: An E.164 formatted phone number or an email address.
          example: '+30123456789'
    Error:
      type: object
      properties:
        code:
          type: string
        message:
          type: string
        type:
          type: string
        request_id:
          type: string
    CreateVerificationRequest:
      type: object
      required:
        - target
      properties:
        target:
          $ref: '#/components/schemas/Target'
        options:
          type: object
          description: Optional verification settings.
          properties:
            template_id:
              type: string
            variables:
              type: object
              additionalProperties:
                type: string
            method:
              type: string
              enum:
                - auto
                - voice
            locale:
              type: string
            sender_id:
              type: string
            app_realm:
              type: object
              additionalProperties: true
            code_size:
              type: integer
            custom_code:
              type: string
            callback_url:
              type: string
              format: uri
            preferred_channel:
              type: string
              enum:
                - sms
                - rcs
                - whatsapp
                - viber
                - voice
            force_challenge:
              type: boolean
          additionalProperties: true
        signals:
          $ref: '#/components/schemas/Signals'
        metadata:
          $ref: '#/components/schemas/Metadata'
        dispatch_id:
          type: string
          description: Identifier of a dispatch created by the Prelude frontend SDK.
    Signals:
      type: object
      description: Anti-fraud signals gathered from the end user's device / session.
      properties:
        ip:
          type: string
        device_id:
          type: string
        device_platform:
          type: string
          enum:
            - android
            - ios
            - web
        device_model:
          type: string
        os_version:
          type: string
        app_version:
          type: string
        user_agent:
          type: string
        ja4_fingerprint:
          type: string
        is_trusted_user:
          type: boolean
      additionalProperties: true
    Metadata:
      type: object
      properties:
        correlation_id:
          type: string
          maxLength: 80
          description: A user-defined identifier to correlate this call with others.
    Verification:
      type: object
      properties:
        id:
          type: string
          example: vrf_01jc0t6fwwfgfsq1md24mhyztj
        status:
          type: string
          enum:
            - success
            - retry
            - challenged
            - blocked
            - shadow_blocked
        method:
          type: string
          enum:
            - email
            - message
            - silent
            - voice
        reason:
          type: string
          description: Populated when status is blocked or shadow_blocked.
        channels:
          type: array
          description: Ordered sequence of delivery channels attempted.
          items:
            type: string
        silent:
          type: object
          additionalProperties: true
        risk_factors:
          type: array
          items:
            type: string
        metadata:
          $ref: '#/components/schemas/Metadata'
        request_id:
          type: string
    CheckVerificationRequest:
      type: object
      required:
        - target
        - code
      properties:
        target:
          $ref: '#/components/schemas/Target'
        code:
          type: string
          description: The one-time passcode submitted by the end user.
        psd2:
          type: object
          description: Transaction details for PSD2 (dynamic linking) verifications.
          properties:
            amount:
              type: string
            currency:
              type: string
            recipient:
              type: string
    VerificationCheck:
      type: object
      properties:
        id:
          type: string
          example: vrf_01jc0t6fwwfgfsq1md24mhyztj
        status:
          type: string
          enum:
            - success
            - failure
            - expired_or_not_found
            - transaction_missing
            - transaction_mismatch
        metadata:
          $ref: '#/components/schemas/Metadata'
        request_id:
          type: string
    LookupResponse:
      type: object
      properties:
        phone_number:
          type: string
        country_code:
          type: string
        network_info:
          $ref: '#/components/schemas/NetworkInfo'
        original_network_info:
          $ref: '#/components/schemas/NetworkInfo'
        flags:
          type: array
          description: Flags such as `ported` or `temporary`.
          items:
            type: string
            enum:
              - ported
              - temporary
        caller_name:
          type: string
          description: CNAM data; requires enablement.
        line_type:
          type: string
          enum:
            - mobile
            - fixed_line
            - voip
            - toll_free
            - premium_rate
            - unknown
    NetworkInfo:
      type: object
      properties:
        carrier_name:
          type: string
        mcc:
          type: string
          description: Mobile Country Code.
        mnc:
          type: string
          description: Mobile Network Code.
    PredictWatchRequest:
      type: object
      required:
        - target
      properties:
        target:
          $ref: '#/components/schemas/Target'
        signals:
          $ref: '#/components/schemas/Signals'
        dispatch_id:
          type: string
          description: Identifier of a dispatch created by the Prelude frontend SDK.
        metadata:
          $ref: '#/components/schemas/Metadata'
    PredictWatchResponse:
      type: object
      properties:
        id:
          type: string
          description: The prediction identifier.
        prediction:
          type: string
          enum:
            - legitimate
            - suspicious
        risk_factors:
          type: array
          description: Present when prediction is suspicious.
          items:
            type: string
            enum:
              - behavioral_pattern
              - device_attribute
              - fraud_database
              - location_discrepancy
              - network_fingerprint
              - poor_conversion_history
              - prefix_concentration
              - suspected_request_tampering
              - suspicious_ip_address
              - temporary_phone_number
        request_id:
          type: string
    FeedbackWatchRequest:
      type: object
      required:
        - feedbacks
      properties:
        feedbacks:
          type: array
          maxItems: 100
          items:
            type: object
            required:
              - target
              - type
            properties:
              target:
                $ref: '#/components/schemas/Target'
              type:
                type: string
                enum:
                  - verification.started
                  - verification.completed
              metadata:
                $ref: '#/components/schemas/Metadata'
    FeedbackWatchResponse:
      type: object
      properties:
        status:
          type: string
          example: success
        request_id:
          type: string
    DispatchEventsRequest:
      type: object
      description: >-
        Modeled request shape; the published documentation references this
        endpoint but did not include its full schema at review time.
      properties:
        dispatch_id:
          type: string
        events:
          type: array
          items:
            type: object
            additionalProperties: true
    SendMessageRequest:
      type: object
      required:
        - to
        - template_id
      properties:
        to:
          type: string
          description: The recipient's phone number in E.164 format.
          example: '+30123456789'
        template_id:
          type: string
          description: Template identifier configured by your Customer Success team.
        from:
          type: string
          description: Sender ID.
        variables:
          type: object
          additionalProperties:
            type: string
        locale:
          type: string
          description: BCP-47 language code.
        schedule_at:
          type: string
          format: date-time
        expires_at:
          type: string
          format: date-time
        callback_url:
          type: string
          format: uri
        correlation_id:
          type: string
          maxLength: 80
        preferred_channel:
          type: string
          enum:
            - sms
            - rcs
            - whatsapp
        document:
          type: object
          properties:
            url:
              type: string
              format: uri
            filename:
              type: string
        max_auto_retries:
          type: integer
          minimum: 0
          maximum: 6
    Message:
      type: object
      properties:
        id:
          type: string
        to:
          type: string
        template_id:
          type: string
        from:
          type: string
        variables:
          type: object
          additionalProperties:
            type: string
        callback_url:
          type: string
          format: uri
        correlation_id:
          type: string
        schedule_at:
          type: string
          format: date-time
        expires_at:
          type: string
          format: date-time
        created_at:
          type: string
          format: date-time
        estimated_segment_count:
          type: integer
        encoding:
          type: string
          enum:
            - GSM-7
            - UCS-2