> ## Documentation Index
> Fetch the complete documentation index at: https://doc.featherhq.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Render a preview (text + blocks) of candidate-or-effective slots



## OpenAPI

````yaml /api-reference/openapi.json post /v1/notifications/types/{event_type}/template/preview
openapi: 3.1.0
info:
  title: Feather API
  description: >-
    Unified customer experience platform API. Manages identity, conversations,
    memory, agents, procedures, policies, model routing, knowledge bases,
    integrations, and runtime execution.
  version: 1.21.0
servers:
  - url: https://api-sandbox.featherhq.com
    description: Sandbox
  - url: http://localhost:8000
    description: Local dev
security: []
paths:
  /v1/notifications/types/{event_type}/template/preview:
    post:
      tags:
        - notifications
      summary: Render a preview (text + blocks) of candidate-or-effective slots
      operationId: previewNotificationTemplate
      parameters:
        - name: event_type
          in: path
          required: true
          schema:
            type: string
            title: Event Type
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/TemplatePreviewRequest'
      responses:
        '200':
          description: Successful Response
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/TemplatePreviewResponse'
        '400':
          description: Bad request
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        '401':
          description: Authentication required
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        '422':
          description: Validation Error
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/HTTPValidationError'
      security:
        - APIKeyHeader: []
components:
  schemas:
    TemplatePreviewRequest:
      properties:
        slots:
          anyOf:
            - $ref: '#/components/schemas/TemplateSlots'
            - type: 'null'
        payload:
          anyOf:
            - $ref: '#/components/schemas/Payload'
            - type: 'null'
      additionalProperties: false
      type: object
      title: TemplatePreviewRequest
    TemplatePreviewResponse:
      properties:
        text:
          type: string
          title: Text
        blocks:
          items:
            additionalProperties: true
            type: object
          type: array
          title: Blocks
        warnings:
          items:
            type: string
          type: array
          title: Warnings
      type: object
      required:
        - text
        - blocks
        - warnings
      title: TemplatePreviewResponse
      description: >-
        Rendered preview. ``blocks`` ARE returned even though v1 delivery is
        text-only.
    ErrorResponse:
      properties:
        error:
          type: string
          title: Error
        message:
          type: string
          title: Message
      type: object
      required:
        - error
        - message
      title: ErrorResponse
      description: Standard error response returned by all API error handlers.
    HTTPValidationError:
      properties:
        detail:
          items:
            $ref: '#/components/schemas/ValidationError'
          type: array
          title: Detail
      type: object
      title: HTTPValidationError
    TemplateSlots:
      properties:
        title:
          type: string
          maxLength: 4000
          minLength: 1
          title: Title
        body:
          type: string
          maxLength: 4000
          title: Body
          default: ''
        fields:
          items:
            $ref: '#/components/schemas/TemplateField'
          type: array
          maxItems: 10
          title: Fields
        link_text:
          anyOf:
            - type: string
              maxLength: 4000
            - type: 'null'
          title: Link Text
        link_url:
          anyOf:
            - type: string
              maxLength: 4000
            - type: 'null'
          title: Link Url
      additionalProperties: false
      type: object
      required:
        - title
      title: TemplateSlots
      description: >-
        The four authorable slots. ``extra="forbid"`` so an operator can't
        smuggle

        unknown keys past validation (mirrors the catalog's threshold configs).
    Payload:
      additionalProperties:
        $ref: '#/components/schemas/JsonValue'
      type: object
    ValidationError:
      properties:
        loc:
          items:
            anyOf:
              - type: string
              - type: integer
          type: array
          title: Location
        msg:
          type: string
          title: Message
        type:
          type: string
          title: Error Type
        input:
          title: Input
        ctx:
          type: object
          title: Context
      type: object
      required:
        - loc
        - msg
        - type
      title: ValidationError
    TemplateField:
      properties:
        label:
          type: string
          maxLength: 4000
          minLength: 1
          title: Label
        value:
          type: string
          maxLength: 4000
          title: Value
      additionalProperties: false
      type: object
      required:
        - label
        - value
      title: TemplateField
      description: One label/value fact line. Both sides are mrkdwn Jinja strings.
    JsonValue: {}
  securitySchemes:
    APIKeyHeader:
      type: apiKey
      in: header
      name: x-api-key

````