> ## Documentation Index > Fetch the complete documentation index at: https://docs.kapso.ai/llms.txt > Use this file to discover all available pages before exploring further. # Invoke function > Execute a deployed serverless function with a custom JSON payload. The request body is forwarded directly to your function code. Request payload structure is completely flexible - send any valid JSON that your function expects. Your function receives the payload as the request body and can parse it however needed. Successful response behavior depends on `invoke_response_mode`: - New functions default to `passthrough`, so Kapso forwards the function response body, success status code, and `Content-Type` directly - Legacy wrapped functions can keep `wrapped`, which preserves the legacy API shape and returns successful JSON results under `data` The function must be in 'deployed' status to be invoked. If the function is in 'draft' or 'error' status, the request will fail with 422 validation error. Authentication: - Private functions require `X-API-Key` - Public Cloudflare functions (`public_endpoint=true`) can be invoked without an API key - Private and unknown functions both return `404` from this route Execution tracking: - All invocations are tracked with timing and request/response data - Failed invocations return an `invocation_id` for debugging - Check function invocation history via GET /functions/{id} (extended view) Error handling: - Function execution errors are captured and returned with details - Errors are truncated to 512 characters for storage - Original error context is preserved in invocation record ## OpenAPI ````yaml /api/platform/v1/openapi-workflows.yaml post /functions/{function_id}/invoke openapi: 3.1.0 info: title: Kapso Platform API – Advanced Resources version: 0.1.0 description: > Build WhatsApp automation workflows and serverless functions. Create multi-step conversation flows, inspect executions, and deploy custom logic. servers: - url: https://api.kapso.ai/platform/v1 description: Production security: - ApiKeyAuth: [] tags: - name: Workflows description: Create and manage conversation workflows and executions - name: Workflow Triggers description: Configure workflow triggers to automate execution - name: Functions description: Manage serverless functions, deployments, and secrets - name: WhatsApp Conversations description: Query WhatsApp conversation data and related resources paths: /functions/{function_id}/invoke: parameters: - name: function_id in: path required: true schema: type: string format: uuid description: Function identifier post: tags: - Functions summary: Invoke function description: > Execute a deployed serverless function with a custom JSON payload. The request body is forwarded directly to your function code. Request payload structure is completely flexible - send any valid JSON that your function expects. Your function receives the payload as the request body and can parse it however needed. Successful response behavior depends on `invoke_response_mode`: - New functions default to `passthrough`, so Kapso forwards the function response body, success status code, and `Content-Type` directly - Legacy wrapped functions can keep `wrapped`, which preserves the legacy API shape and returns successful JSON results under `data` The function must be in 'deployed' status to be invoked. If the function is in 'draft' or 'error' status, the request will fail with 422 validation error. Authentication: - Private functions require `X-API-Key` - Public Cloudflare functions (`public_endpoint=true`) can be invoked without an API key - Private and unknown functions both return `404` from this route Execution tracking: - All invocations are tracked with timing and request/response data - Failed invocations return an `invocation_id` for debugging - Check function invocation history via GET /functions/{id} (extended view) Error handling: - Function execution errors are captured and returned with details - Errors are truncated to 512 characters for storage - Original error context is preserved in invocation record operationId: invokeFunction requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/FunctionInvokeRequest' examples: shipping_calculation: summary: Calculate shipping cost value: weight: 5.5 distance: 120 service: express data_transformation: summary: Transform user data value: user_id: usr_123 fields: - email - name - phone format: csv responses: '200': description: > Function executed successfully. `wrapped` functions return successful JSON under `data`. `passthrough` functions may also return other 2xx status codes and non-JSON content types depending on the function response. content: application/json: schema: oneOf: - $ref: '#/components/schemas/FunctionInvokeResponse' - $ref: '#/components/schemas/FunctionInvokeWrappedResponse' examples: shipping_result: summary: Passthrough JSON result value: cost: 24.75 currency: USD estimated_days: 2 wrapped_shipping_result: summary: Wrapped JSON result value: data: cost: 24.75 currency: USD estimated_days: 2 text/plain: schema: type: string example: accepted '400': description: Invalid JSON in request body content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: error: Invalid JSON in request '404': description: >- Function not found, or private function is not accessible with the provided API key content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: error: Function not found '422': description: Function is not deployed or validation error content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: error: Function is not deployed '500': description: Function execution failed content: application/json: schema: type: object required: - error properties: error: type: string description: Error message detail: type: string description: >- Detailed error information from function execution (if available) invocation_id: type: string format: uuid description: Invocation record ID for debugging example: error: Function execution failed detail: 'ReferenceError: calculateShipping is not defined' invocation_id: 550e8400-e29b-41d4-a716-446655440000 security: - ApiKeyAuth: [] - {} components: schemas: FunctionInvokeRequest: type: object description: > Payload to send to the function. Structure is completely flexible - send any valid JSON that your function expects. The payload will be forwarded to your function as the request body. additionalProperties: true example: weight: 5.5 distance: 120 service: express FunctionInvokeResponse: description: > Successful invoke output for functions using `invoke_response_mode=passthrough`. Kapso forwards the upstream response body directly and preserves the upstream success status code and `Content-Type`. oneOf: - type: object additionalProperties: true - type: array items: {} - type: string - type: number - type: boolean example: cost: 24.75 currency: USD FunctionInvokeWrappedResponse: type: object required: - data properties: data: description: > Successful invoke output for functions using `invoke_response_mode=wrapped`. Kapso preserves the legacy API shape by nesting successful JSON responses under `data`. oneOf: - type: object additionalProperties: true - type: array items: {} - type: string - type: number - type: boolean example: data: cost: 24.75 currency: USD ErrorResponse: type: object required: - error properties: error: type: string description: Human-readable error message securitySchemes: ApiKeyAuth: type: apiKey in: header name: X-API-Key ````