> ## Documentation Index > Fetch the complete documentation index at: https://docs.prophia.com/llms.txt > Use this file to discover all available pages before exploring further. # CREATE Custom Field > Creates a Building Custom Field on the Account. A `MULTI` field is created with its options. **Required capabilities:** `WRITE:CUSTOM_FIELD` ## OpenAPI ````yaml /api-reference/openapi.json post /rest/v2/accounts/{accountId}/custom-fields openapi: 3.1.0 info: title: Prophia API Documentation license: name: Apache 2.0 url: http://springdoc.org version: v2.495.0 servers: - url: https://api.prophia.com description: Prophia API security: - apiKey: [] tags: - name: Accounts description: >- Accounts are the top-level scope for everything in the API. Start here: list your accounts to find the `accountId` every other path requires. - name: Properties description: >- Properties group one or more buildings under a single asset within an account. - name: Buildings description: Buildings are the physical structures where leases and spaces live. - name: Building Spaces description: >- Building spaces are the units inside a building — suites, floors, storage. A space's `suiteNumber` is the canonical name that tag `applicableSpaces` entries reference by string match. - name: Leases description: >- Leases are the agreements occupying building spaces. Each lease carries its source documents and the tags (structured terms) extracted from them. - name: Documents description: >- Documents are the source files attached to leases — original leases, amendments, memorandums, etc. - name: Tags description: >- Tags are the structured lease terms Prophia extracts from documents — a rent amount, a renewal option, a key date — each cited to its location in the source document. STANDARD tags carry a typed `value`; COMPLEX tags carry option details in `tagComponents`. - name: Custom Terms description: >- Custom terms are account-level definitions of extra lease terms your team tracks beyond Prophia's standard set. Tags created from them are ordinary tags with `isCustomTag: true` — the definition and its tag instances are separate resources. - name: Custom Fields description: >- Custom Fields are Account-level fields your team tracks on Buildings beyond Prophia's standard set. A `SINGLE` field holds free text per Building; a `MULTI` field holds one of a fixed list of options. Assignments set a field's value on a Building. - name: Loans description: >- Loans are the financing agreements secured by an account's buildings. Each loan carries its source documents and the terms read from them: summary terms, covenants and reporting deliverables. Loans is a Labs feature in beta, and its endpoints may change. x-beta: true paths: /rest/v2/accounts/{accountId}/custom-fields: post: tags: - Custom Fields summary: CREATE Custom Field description: >- Creates a Building Custom Field on the Account. A `MULTI` field is created with its options. **Required capabilities:** `WRITE:CUSTOM_FIELD` operationId: createCustomField parameters: - name: accountId in: path required: true schema: type: string requestBody: content: application/json: schema: $ref: '#/components/schemas/V2CreateCustomFieldRequest' required: true responses: '200': description: OK content: '*/*': schema: $ref: '#/components/schemas/V2CustomFieldModel' '400': description: Invalid input — request body failed validation or business rules content: application/json: schema: $ref: '#/components/schemas/V2ErrorResponse' example: error: Invalid Input errorCode: InvalidInput message: dba cannot be blank status: 400 BAD_REQUEST timestamp: '2026-09-02T20:41:03.118Z' localizedMessage: dba cannot be blank '401': description: >- The credential was rejected before the request reached the endpoint — for example a JWT was presented where an API key is required. Only `error` is populated on this path content: application/json: schema: $ref: '#/components/schemas/V2ErrorResponse' example: error: JWT authentication is not supported. Use an API key. '403': description: >- The API key is valid but lacks a required capability or role, the account does not have the REST write module enabled, or the key's building permissions do not cover the requested resource. The message names the missing capabilities only in the first case content: application/json: schema: $ref: '#/components/schemas/V2ErrorResponse' example: error: Access Denied errorCode: AccessDenied message: 'Not authorized. Missing capabilities: WRITE:DOCUMENT' status: 403 FORBIDDEN timestamp: '2026-09-02T20:41:03.118Z' localizedMessage: 'Not authorized. Missing capabilities: WRITE:DOCUMENT' '404': description: No such resource is visible to the account named in the path content: application/json: schema: $ref: '#/components/schemas/V2ErrorResponse' example: error: Entity Not Found errorCode: EntityNotFound message: This entity is not found in the system. status: 404 NOT_FOUND timestamp: '2026-09-02T20:41:03.118Z' localizedMessage: This entity is not found in the system. components: schemas: V2CreateCustomFieldRequest: type: object description: Fields for creating a Building Custom Field on an Account. properties: fieldName: type: string description: >- Name of the field. Must be unique among the Account's Custom Fields, ignoring case, and cannot be `No Value`. minLength: 1 fieldType: type: string description: >- `SINGLE` fields hold free text per Building. `MULTI` fields hold one of a fixed list of `options`. enum: - SINGLE - MULTI active: type: boolean description: Whether the field is shown on Buildings. Defaults to `true`. options: type: array description: >- The choices for a `MULTI` field; at least one is required, and values must be unique ignoring case. Not accepted for `SINGLE` fields, whose values are set through assignments. items: type: string required: - fieldName - fieldType V2CustomFieldModel: type: object description: >- An Account-level field your team tracks on Buildings beyond Prophia's standard set. properties: id: type: string description: Prophia internal Custom Field ID (UUID). readOnly: true accountId: type: string description: The UUID for the Account this Custom Field belongs to. readOnly: true fieldName: type: string description: Name of the field. fieldType: type: string description: >- `SINGLE` fields hold free text per Building. `MULTI` fields hold one of a fixed list of `options`. enum: - SINGLE - MULTI readOnly: true active: type: boolean description: Whether the field is shown on Buildings. options: type: array description: The field's current options. items: $ref: '#/components/schemas/V2CustomFieldOptionModel' readOnly: true createdBy: type: string description: The user who created the field. readOnly: true createdAt: type: string format: date-time description: When the field was created. readOnly: true updatedAt: type: string format: date-time description: When the field was last modified. readOnly: true V2ErrorResponse: type: object properties: error: type: string description: Stable error category example: Invalid Input errorCode: type: string description: Stable error code suitable for programmatic handling example: InvalidInput message: type: string description: Human-readable detail; may aggregate multiple field errors status: type: string description: >- HTTP status of the response as code and reason phrase, matching the response's own status line example: 404 NOT_FOUND timestamp: type: string format: date-time description: When the error was produced, as an ISO-8601 UTC instant example: '2026-09-02T20:41:03.118Z' localizedMessage: type: string description: >- Same text as `message`; present because the body is a serialized exception. Prefer `message` V2CustomFieldOptionModel: type: object description: >- A value of a Building Custom Field. On `MULTI` fields these are the fixed choices; on `SINGLE` fields they are the distinct values assigned to Buildings. properties: id: type: string description: Prophia internal Custom Field Option ID (UUID). readOnly: true value: type: string description: The option's value. createdAt: type: string format: date-time description: When the option was created. readOnly: true updatedAt: type: string format: date-time description: When the option was last modified. readOnly: true securitySchemes: apiKey: type: apiKey description: >- Prophia API key — either an account key (grants admin level permissions) or a user key with the REST scope. Send it in the `X-API-Key` header, or equivalently as `Authorization: Bearer `. JWTs are rejected on /rest endpoints with 401. name: X-API-Key in: header ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.