> ## Documentation Index > Fetch the complete documentation index at: https://docs.promptlayer.com/llms.txt > Use this file to discover all available pages before exploring further. # Add Column to Evaluation Pipeline This endpoint adds evaluation steps (columns) to an existing evaluation pipeline. Columns execute sequentially from left to right, with each column able to reference outputs from previous columns. ## Important Notes * **Single Column Per Request**: This endpoint only allows adding one column at a time. To add multiple columns, make separate API calls for each. * **Column Order Matters**: Columns execute left to right. A column can only reference columns to its left. * **Unique Names Required**: Each column name must be unique within the pipeline. * **Dataset Columns Protected**: You cannot overwrite columns that come from the dataset. ## Scoring By default, only the last column in a pipeline is used for score calculation. To include multiple columns in the final score: * Set `is_part_of_score: true` on each column you want to include in the score * Columns must produce boolean or numeric values to be scored * When multiple columns are marked for scoring, the final score is the average of all included columns ## Column Types and Configuration For the complete list of supported column types and their detailed configuration options, see the [Node & Column Types](/features/evaluations/column-types) documentation. ## Batch Adding Columns Since columns must be added one at a time, here's a pattern for adding multiple columns: ```python theme={null} import requests columns = [ { "column_type": "PROMPT_TEMPLATE", "name": "Generate", "configuration": {...} }, { "column_type": "LLM_ASSERTION", "name": "Validate", "configuration": {...} } ] for column in columns: response = requests.post( "https://api.promptlayer.com/report-columns", headers={"X-API-KEY": "your_key"}, json={ "report_id": 456, **column } ) if response.status_code != 201: print(f"Failed: {column['name']}") break ``` ## Column Reference Syntax When configuring columns that reference other columns: * **Dataset columns**: Use exact column name from dataset (e.g., `"question"`) * **Previous columns**: Use the name you assigned (e.g., `"AI Response"`) * **Variable columns**: Reference by their name ## Error Handling The endpoint validates: 1. Column type is valid 2. Column name is unique within the pipeline 3. Configuration matches the column type schema 4. Referenced columns exist (for dependent columns) 5. User has permission to modify the pipeline Common errors: * `400`: Invalid configuration or duplicate column name * `403`: Cannot overwrite dataset columns or lacking permissions * `404`: Report not found or not accessible ## OpenAPI ````yaml POST /report-columns openapi: 3.1.0 info: title: FastAPI version: 0.1.0 servers: [] security: - ApiKeyAuth: [] paths: /report-columns: post: tags: - reports summary: Add Column to Evaluation Pipeline operationId: addReportColumn requestBody: required: true content: application/json: schema: type: object properties: report_id: type: integer description: The ID of the evaluation pipeline to add this column to. minimum: 1 column_type: type: string description: >- The type of evaluation or transformation this column performs. Must be one of the supported column types. enum: - ABSOLUTE_NUMERIC_DISTANCE - AI_DATA_EXTRACTION - ASSERT_VALID - CONVERSATION_SIMULATOR - COALESCE - CODE_EXECUTION - COMBINE_COLUMNS - COMPARE - CONTAINS - COSINE_SIMILARITY - COUNT - ENDPOINT - MCP - HUMAN - JSON_PATH - LLM_ASSERTION - MATH_OPERATOR - MIN_MAX - PARSE_VALUE - APPLY_DIFF - PROMPT_TEMPLATE - REGEX - REGEX_EXTRACTION - VARIABLE - XML_PATH - WORKFLOW - CODING_AGENT name: type: string description: >- Display name for this column. Must be unique within the pipeline. This name is used to reference the column in subsequent steps. minLength: 1 maxLength: 255 configuration: type: object description: >- Column-specific configuration. The schema varies based on column_type. See documentation for each type's requirements. additionalProperties: true position: type: integer description: >- Optional position for the column. If not specified, the column is added at the end. Cannot overwrite dataset columns. minimum: 0 nullable: true required: - report_id - column_type - name - configuration example: report_id: 456 column_type: PROMPT_TEMPLATE name: Generate Answer configuration: template: name: qa_template version_number: null prompt_template_variable_mappings: question: input_question engine: provider: openai model: gpt-4 parameters: temperature: 0.7 responses: '201': description: Column added successfully content: application/json: schema: type: object properties: success: type: boolean example: true report_column: type: object description: >- Details of the created column including its ID and configuration '400': description: >- Bad Request - Invalid column type, configuration validation failed, or column name already exists content: application/json: schema: type: object properties: success: type: boolean example: false message: type: string example: Report already has a column with that name '401': description: Unauthorized - Invalid or missing authentication '403': description: Forbidden - Cannot overwrite dataset columns or missing permissions content: application/json: schema: type: object properties: success: type: boolean example: false message: type: string example: You can not overwrite dataset columns '404': description: Not Found - Report not found or not accessible content: application/json: schema: type: object properties: success: type: boolean example: false message: type: string example: Report not found '422': $ref: '#/components/responses/ValidationError' components: responses: ValidationError: description: Validation error - request parameters or body are invalid. content: application/json: schema: oneOf: - $ref: '#/components/schemas/HTTPValidationError' - $ref: '#/components/schemas/ErrorResponse' schemas: HTTPValidationError: properties: detail: items: $ref: '#/components/schemas/ValidationError' type: array title: Detail type: object title: HTTPValidationError ErrorResponse: type: object properties: success: type: boolean default: false description: Indicates that the request failed. message: type: string description: Human-readable error message. error: type: string description: Machine-readable or fallback error message. additionalProperties: true description: >- Standard error response. Some legacy endpoints may return either message or error. ValidationError: properties: loc: items: anyOf: - type: string - type: integer type: array title: Location msg: type: string title: Message type: type: string title: Error Type type: object required: - loc - msg - type title: ValidationError securitySchemes: ApiKeyAuth: type: apiKey in: header name: X-API-KEY ````