> ## Documentation Index > Fetch the complete documentation index at: https://docs.braintrust.dev/llms.txt > Use this file to discover all available pages before exploring further. # List custom columns > List the custom columns defined for a table. Requires read permission on the scoping object. Custom columns are scoped to a specific table by the combination of `object_type`, `object_id`, `subtype`, and `variant`. Use the same scope when creating and listing columns. Use these combinations to display columns in the corresponding UI table: | Page | `object_type` | `object_id` | `subtype` | `variant` | | --- | --- | --- | --- | --- | | Dataset | `dataset` | Dataset ID | `""` | `dataset` | | Project logs | `project` | Project ID | `project_log` | `project_log` | | Experiment details | `project` | Project ID | `experiment` | `experiment` | | Experiments list | `project` | Project ID | `experiment` | `experiment_list` | Experiment span columns apply across experiments in the project. ## OpenAPI ````yaml /openapi.yaml get /v1/column openapi: 3.1.1 info: version: 1.0.0 title: Braintrust API description: >- API specification for the backend data server. The API is hosted globally at https://api.braintrust.dev or in your own environment. You can access the OpenAPI spec for this API at https://github.com/braintrustdata/braintrust-openapi. license: name: Apache 2.0 servers: - url: https://api.braintrust.dev security: - bearerAuth: [] - {} paths: /v1/column: get: tags: - CustomColumns summary: List custom columns description: >- List the custom columns defined for a table. Requires read permission on the scoping object. Custom columns are scoped to a specific table by the combination of `object_type`, `object_id`, `subtype`, and `variant`. Use the same scope when creating and listing columns. Use these combinations to display columns in the corresponding UI table: | Page | `object_type` | `object_id` | `subtype` | `variant` | | --- | --- | --- | --- | --- | | Dataset | `dataset` | Dataset ID | `""` | `dataset` | | Project logs | `project` | Project ID | `project_log` | `project_log` | | Experiment details | `project` | Project ID | `experiment` | `experiment` | | Experiments list | `project` | Project ID | `experiment` | `experiment_list` | Experiment span columns apply across experiments in the project. operationId: getCustomColumn parameters: - schema: type: string enum: - organization - project - experiment - dataset - prompt - prompt_session - group - role - org_member - project_log - org_project - org_audit_logs - project_group - project_group_projects - ai_secret - org_ai_secret - org_account description: >- The type of the object the custom column is scoped to, usually `project` required: true description: >- The type of the object the custom column is scoped to, usually `project` name: object_type in: query - schema: type: string format: uuid description: >- The ID of the scoping object. Use the project ID for project logs, experiment spans, and the experiments list. Use the dataset ID for dataset rows required: true description: >- The ID of the scoping object. Use the project ID for project logs, experiment spans, and the experiments list. Use the dataset ID for dataset rows name: object_id in: query - schema: anyOf: - $ref: '#/components/schemas/AclObjectType' - type: string enum: - '' description: >- The child object type the custom column applies to, such as `experiment` or `project_log`. Use an empty string when the column applies directly to the scoping object, such as a dataset required: false description: >- The child object type the custom column applies to, such as `experiment` or `project_log`. Use an empty string when the column applies directly to the scoping object, such as a dataset name: subtype in: query - schema: allOf: - $ref: '#/components/schemas/CustomColumnVariant' - description: >- The table variant the custom column applies to. If omitted, defaults to the nonempty `subtype`, or otherwise to `object_type`. Set `experiment_list` explicitly to target the experiments list instead of experiment details. Use the same scope when creating and listing columns required: false description: >- The table variant the custom column applies to. If omitted, defaults to the nonempty `subtype`, or otherwise to `object_type`. Set `experiment_list` explicitly to target the experiments list instead of experiment details. Use the same scope when creating and listing columns name: variant in: query responses: '200': description: Returns a list of custom column objects content: application/json: schema: type: object properties: objects: type: array items: $ref: '#/components/schemas/CustomColumn' required: - objects '400': description: >- The request was unacceptable, often due to missing a required parameter content: text/plain: schema: type: string application/json: schema: {} '401': description: No valid API key provided content: text/plain: schema: type: string application/json: schema: {} '403': description: The API key doesn’t have permissions to perform the request content: text/plain: schema: type: string application/json: schema: {} '429': description: >- Too many requests hit the API too quickly. We recommend an exponential backoff of your requests headers: Retry-After: schema: type: string content: text/plain: schema: type: string application/json: schema: {} '500': description: Something went wrong on Braintrust's end. (These are rare.) content: text/plain: schema: type: string application/json: schema: {} security: - bearerAuth: [] - {} components: schemas: AclObjectType: type: string enum: - organization - project - experiment - dataset - prompt - prompt_session - group - role - org_member - project_log - org_project - org_audit_logs - project_group - project_group_projects - ai_secret - org_ai_secret - org_account description: The object type that the ACL applies to CustomColumnVariant: type: string enum: - project - experiment - dataset - project_log - experiment_list description: The table variant that the custom column applies to CustomColumn: type: object properties: id: type: string format: uuid description: Unique identifier for the custom columns object_type: $ref: '#/components/schemas/AclObjectType' object_id: type: string format: uuid description: The id of the object the custom column is scoped for subtype: anyOf: - $ref: '#/components/schemas/AclObjectType' - type: string enum: - '' description: The object type that the ACL applies to variant: $ref: '#/components/schemas/CustomColumnVariant' name: type: string description: The name of the custom column expr: type: string description: The expression used to extract the value for the custom column created: type: - string - 'null' format: date-time description: Date of custom columns creation required: - id - object_type - object_id - subtype - variant - name - expr securitySchemes: bearerAuth: type: http scheme: bearer bearerFormat: API key or JWT description: >- Most Braintrust endpoints are authenticated by providing your API key as a header `Authorization: Bearer [api_key]` to your HTTP request. You can create an API key in the Braintrust [organization settings page](https://www.braintrustdata.com/app/settings?subroute=api-keys). ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.