> ## Documentation Index > Fetch the complete documentation index at: https://help.withallo.com/llms.txt > Use this file to discover all available pages before exploring further. # Create custom field > Creates a custom field on your team's people. The key is derived from the label. Creating the same label with the same type again returns the existing field with `already_existed` set to `true`. **Required scope:** `CRM_WRITE` ## Body fields | Field | Type | Required | Description | | - | - | - | - | | `label` | string | yes | Display name, 1 to 255 characters, with at least one letter or digit | | `type` | string | yes | `TEXT`, `NUMBER`, `DATE` or `BOOLEAN` | `DROPDOWN` fields are synced from your CRM integrations and cannot be created here. ## Key derivation The `key` is derived from the label: lowercase, accents removed, runs of non-alphanumeric characters replaced by `_`, truncated to 64 characters. `Lead Source` becomes `lead_source`. A label that resolves to a built-in field key is rejected with `ATTRIBUTE_KEY_RESERVED`. The reserved keys are `name`, `phone_numbers`, `company`, `job_title`, `emails`, `last_activity`, `website`, `created_at` and `updated_at`. ## Creating the same field twice The call is safe to repeat. If a field with the same key and type already exists, the endpoint returns `201` with `already_existed` set to `true` and the label it was first created with. Nothing is created. ```json theme={null} { "data": { "key": "lead_source", "label": "Lead Source", "type": "TEXT", "already_existed": true } } ``` If the key exists with a different type, the request returns `409 ATTRIBUTE_KEY_CONFLICT`. ## Limits A team can hold up to 150 `TEXT`, 50 `NUMBER`, 30 `DATE` and 30 `BOOLEAN` custom fields. Once a type is full, creating another field of that type returns `409 ATTRIBUTE_SLOTS_EXHAUSTED`. ## Errors | Status | Code | When | | - | - | - | | `400` | `ATTRIBUTE_LABEL_INVALID` | `label` is blank, longer than 255 characters, or has no letter or digit | | `400` | `ATTRIBUTE_KEY_RESERVED` | The label resolves to a built-in field key | | `400` | `INVALID_REQUEST_BODY` | `type` is missing or is not one of `TEXT`, `NUMBER`, `DATE`, `BOOLEAN` | | `403` | `API_KEY_INSUFFICIENT_SCOPE` | The key does not hold `CRM_WRITE` | | `404` | `TEAM_NOT_FOUND` | The workspace is not on the new contact model | | `409` | `ATTRIBUTE_KEY_CONFLICT` | A field with this key already exists with another type | | `409` | `ATTRIBUTE_SLOTS_EXHAUSTED` | No free slot is left for this type | ## OpenAPI ````yaml POST /v2/api/crm/attributes openapi: 3.0.3 info: title: Allo API description: >- Allo API provides programmatic access to your Allo account, allowing you to manage webhooks, retrieve calls and contacts, and send SMS messages. All requests to `/v1/api/**` endpoints automatically go through quota checking and scope validation. version: 1.0.0 contact: name: Allo Support servers: - url: https://api.withallo.com description: Production server security: [] tags: - name: Summary Templates description: >- Manage call summary templates that control how AI-generated call summaries are structured for your team. - name: Webhooks description: >- Manage webhook endpoints to receive real-time notifications about events in your Allo account. Each endpoint subscribes to one or more event topics and is verified with a signing secret. - name: Calls description: >- Retrieve and search call records with filtering and pagination. Filter calls by your Allo phone number. - name: Contacts description: >- Search and retrieve contact information with sorting and pagination. Includes engagement level tracking. - name: SMS description: Send SMS messages to phone numbers using your Allo numbers. - name: Phone Numbers description: Retrieve information about your Allo phone numbers. - name: Analytics description: Pre-computed call metrics, team performance, and outbound dial funnel - name: CRM description: Manage people, companies, and deals in your CRM. - name: Notes description: >- Internal team notes on conversations and CRM people, with @mention support. Notes are never visible to the contact. - name: Threads description: >- Team discussion threads attached to a conversation item (call, SMS, or conversation note). One thread per item. - name: AI Receptionist description: >- Read and write the AI receptionist configuration of a phone line: business details, voice, prompt, capabilities, business hours, transfer rules, scheduling calendars and knowledge sources. paths: /v2/api/crm/attributes: post: tags: - CRM summary: Create custom contact field description: >- Creates a custom field on your team's people. The key is derived from the label. Creating the same label with the same type again returns the existing field with `already_existed` set to `true`. operationId: createCrmAttribute requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/CreateCrmAttributeRequest' example: label: Lead Source type: TEXT responses: '201': description: The custom field that was created, or the existing one content: application/json: schema: type: object properties: data: $ref: '#/components/schemas/CreateCrmAttributeResult' example: data: key: lead_source label: Lead Source type: TEXT already_existed: false '400': $ref: '#/components/responses/ApiValidationError' '401': $ref: '#/components/responses/ApiUnauthorized' '403': $ref: '#/components/responses/ApiForbidden' '404': $ref: '#/components/responses/ApiNotFound' '409': $ref: '#/components/responses/ApiConflict' '429': $ref: '#/components/responses/ApiRateLimited' security: - ApiKeyAuth: [] components: schemas: CreateCrmAttributeRequest: type: object description: Request body for creating a custom contact field required: - label - type properties: label: type: string minLength: 1 maxLength: 255 description: >- Display name of the field. The key is derived from it: lowercase, accents removed, runs of non-alphanumeric characters replaced by `_`, truncated to 64 characters. Must contain at least one letter or digit and must not resolve to a built-in field key such as `name`, `company` or `website`. example: Lead Source type: type: string enum: - TEXT - NUMBER - DATE - BOOLEAN description: Value type of the field example: TEXT CreateCrmAttributeResult: type: object properties: key: type: string description: Key derived from the label example: lead_source label: type: string description: >- Stored label. When the field already existed, this is the label it was first created with. example: Lead Source type: type: string enum: - TEXT - NUMBER - DATE - BOOLEAN example: TEXT already_existed: type: boolean description: >- `true` when a field with the same key and type already existed and nothing was created example: false ApiError: type: object properties: error: type: object properties: type: type: string code: type: string message: type: string retryable: type: boolean request_id: type: string retry_after_seconds: type: integer nullable: true responses: ApiValidationError: description: Invalid request parameters content: application/json: schema: $ref: '#/components/schemas/ApiError' ApiUnauthorized: description: Invalid or missing API key content: application/json: schema: $ref: '#/components/schemas/ApiError' ApiForbidden: description: API key lacks the required scope or access to the resource content: application/json: schema: $ref: '#/components/schemas/ApiError' ApiNotFound: description: Resource not found content: application/json: schema: $ref: '#/components/schemas/ApiError' ApiConflict: description: Conflict with existing resource content: application/json: schema: $ref: '#/components/schemas/ApiError' ApiRateLimited: description: Rate limit exceeded content: application/json: schema: $ref: '#/components/schemas/ApiError' securitySchemes: ApiKeyAuth: type: apiKey in: header name: Authorization ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.