> ## Documentation Index > Fetch the complete documentation index at: https://vexioncards.mintlify.site/llms.txt > Use this file to discover all available pages before exploring further. # Retrieve a custom field > Returns one field definition with live usage bookkeeping (`usage_count`, `cards_using[]`). Scope: `custom_fields:read`. Check usage before attempting structural edits: while any card references the field, `key` renames, `field_type` changes, and option-value removals return `409 custom_field_in_use` - labels, translations, position, and ADDING options stay editable at any time. ## OpenAPI ````yaml /openapi.json get /v1/custom_fields/{id} openapi: 3.1.0 info: title: VEXiON cards Public API description: >- ## Rate limiting Two independent layers, checked in this order: 1. **Per-IP throttle (pre-authentication).** Applied to every `/v1` request BEFORE the API key is checked, keyed on the caller's IP address: - **600 requests/minute** per IP - a flood ceiling, `429 rate_limit_error` / `rate_limited`. - **20 failed authentications per 15 minutes** per IP - a key-guessing ceiling. Only responses that are `401` (missing/invalid/revoked key) count against this ceiling; a `403` from a valid key that simply lacks a scope does not. `429 rate_limit_error` / `too_many_failed_attempts`. Both ceilings send `Retry-After` (seconds). 2. **Per-key, per-bucket limiter (post-authentication).** Documented per endpoint (see each operation's `429` response and the `rate_limit` field on the API Key resource) - e.g. 60/min default, 120/min for transactions, plus the notification-broadcast and lookup-filter buckets described on their own endpoints. ### Rate-limit response headers Every rate-limited response carries the legacy `X-RateLimit-Limit` / `X-RateLimit-Remaining` / `X-RateLimit-Reset` family (the last is an **epoch timestamp**) AND the IETF standards-track headers, side by side: - `RateLimit-Policy: "";q=;w=` - the static policy for the bucket that was hit. - `RateLimit: "";r=;t=` - live state. **`t` is a DURATION (seconds remaining), not the epoch timestamp `X-RateLimit-Reset` carries - the two are never the same value.** version: 1.0.0 servers: - url: https://api.vexioncards.one description: Production - url: https://migration.api.vexioncards.one description: Sandbox security: - apiKey: [] tags: - name: Customers - name: Cards - name: Transactions - name: Notifications - name: Locations - name: Products - name: API keys - name: Organization - name: Webhook endpoints - name: Events - name: Custom fields - name: Team members - name: Icons paths: /v1/custom_fields/{id}: get: tags: - Custom fields summary: Retrieve a custom field description: >- Returns one field definition with live usage bookkeeping (`usage_count`, `cards_using[]`). Scope: `custom_fields:read`. Check usage before attempting structural edits: while any card references the field, `key` renames, `field_type` changes, and option-value removals return `409 custom_field_in_use` - labels, translations, position, and ADDING options stay editable at any time. operationId: getCustomField parameters: - name: id in: path description: Custom field identifier (`cf_` prefix). required: true example: cf_jlgwnmefr6tum774axsvz677py schema: type: string pattern: ^cf_[A-Za-z0-9]+$ responses: '200': description: The custom field object. content: application/json: schema: $ref: '#/components/schemas/CustomField' examples: Field: summary: In use by 3 cards value: id: cf_01HW9R9Z4EF7N8MTX1RVCFLD01 object: custom_field key: department description: Clinic department the patient is assigned to. field_type: select position: 2 options: - value: cardio label: Cardiology - value: neuro label: Neurology - value: ortho label: Orthopedics date_granularity: date usage_count: 3 cards_using: - crd_l47u555jitul2m63lryijy4wya - crd_eyua5rb6gzr3jtydy3fgbhcgpy - crd_pkmywxjb63cng2aupvzyymxuzm created_at: 1750000000 updated_at: 1750000000 label: sk: Oddelenie en: Department headers: {} '401': description: Unauthorized content: application/json: schema: $ref: '#/components/schemas/Error' headers: {} '403': description: Forbidden content: application/json: schema: $ref: '#/components/schemas/Error' headers: {} '404': description: Not found content: application/json: schema: $ref: '#/components/schemas/Error' headers: {} '429': description: Rate limited - respect Retry-After. content: application/json: schema: $ref: '#/components/schemas/Error' '500': description: Server error. Retry-safe on idempotent calls. content: application/json: schema: $ref: '#/components/schemas/Error' example: error: type: api_error code: internal_error message: >- An internal error occurred. The request may be retried with the same Idempotency-Key. doc_url: >- https://vexioncards.mintlify.site/api-reference/errors#internal_error request_id: req_5f8b2c4a9e1d3 examples: Http 500 default: summary: Http 500 default value: error: type: api_error code: internal_error message: >- An internal error occurred. The request may be retried with the same Idempotency-Key. doc_url: >- https://vexioncards.mintlify.site/api-reference/errors#internal_error request_id: req_5f8b2c4a9e1d3 headers: {} deprecated: false components: schemas: CustomField: type: object description: >- A reusable custom field DEFINITION - the single vocabulary used across the whole platform: the signup form (via each card's `form_builder`), the customer record (`Customer.custom.`), wallet pass slots (`{{custom.}}` in `Card.pass_fields`), and notification templates. Define once, reference everywhere. The definition owns IDENTITY (key, type, options, granularity) and DEFAULTS (label translations, required, position); each card's form owns USAGE (which fields, per-card required/order/label overrides). Limits: 50 definitions per organization (`409 custom_field_limit_reached`), 20 fields per card form. required: - id - object - key - label - field_type - created_at properties: id: type: string pattern: ^cf_[A-Za-z0-9]+$ description: Opaque, stable, immutable. `cf_` prefix. example: cf_01HW9R9Z4EF7N8MTX1RVCFLD01 object: type: string const: custom_field description: Always `"custom_field"`. key: type: string pattern: ^[a-z][a-z0-9_]{1,49}$ description: >- Stable machine identifier, unique within the organization (2-50 chars, lowercase snake). Used in `{{custom.}}` templates and Customer `custom.` payloads. **Renames are blocked while the field is in use** (usage_count > 0) to prevent keys diverging across cards. example: department label: anyOf: - type: string title: Single label (all languages) minLength: 1 maxLength: 200 - type: object title: Per-language labels additionalProperties: type: string minLength: 1 maxLength: 200 minProperties: 1 description: >- Keys are language codes (`sk`, `cs`, `en`, `de`, `hu`, `hr`, `ro`). On write this collapses immediately to a single stored string - `en` if present, otherwise the first language present - it is not resolved per customer language at read time. Real per-language display lives per CARD: see `Card.formBuilder.fields[].translations[]`. description: >- Customer-facing label - shown on the signup form, referenced on wallet passes, and used in the dashboard. Plain string or per-language object (the platform localization pattern, same as `Card.name`). This is the DEFAULT - each card's `form_builder` can override the label per card. description: type: - string - 'null' maxLength: 500 description: Internal helper text for the dashboard. example: Clinic department the patient is assigned to. field_type: type: string enum: - text - textarea - number - currency - date - boolean - select - multiselect description: >- What kind of data the field holds - drives form input, validation, and typed pass/notification rendering: | type | value shape | pass rendering | |---|---|---| | `text` | string ≤200 | as-is | | `textarea` | string ≤2000 | back of pass only | | `number` | number (`number_format` controls integer vs decimal) | locale-formatted number | | `currency` | integer, minor units, organization currency | locale-formatted amount (native on Apple via ISO 4217; server-formatted on Google) | | `date` | string per `date_granularity` (`YYYY` / `YYYY-MM` / `YYYY-MM-DD`) | locale-formatted date | | `boolean` | true / false | localized Yes/No | | `select` | one option `value` | the option's label, customer language | | `multiselect` | array of option `value`s | comma-joined labels | Immutable while the field is used by any card (`409 custom_field_in_use`). example: select position: type: integer description: >- DEFAULT form position when added to a card; each card's `form_builder` ordering overrides. example: 2 options: type: array items: type: object properties: value: type: string description: >- Stored machine value - immutable once any customer has stored it. label: anyOf: - type: string title: Single label (all languages) minLength: 1 maxLength: 100 - type: object title: Per-language labels additionalProperties: type: string minLength: 1 maxLength: 100 minProperties: 1 description: >- Keys are language codes (`sk`, `cs`, `en`, `de`, `hu`, `hr`, `ro`). On write this collapses immediately to a single stored string - `en` if present, otherwise the first language present - it is not resolved per customer language at read time. Real per-language display lives per CARD: see `Card.formBuilder.fields[].translations[]`. description: >- Display label for the option - localizable; shown on the form and rendered on passes/notifications in the customer's language. Always editable. description: >- Choices for `select` / `multiselect` (required for those types). Each option is `{value, label}` - **labels are always editable** (display only); **values are immutable once any customer has stored them** and removing a used value is blocked (`409 custom_field_in_use`). Adding options is always allowed. example: - value: cardio label: Cardiology - value: neuro label: Neurology date_granularity: type: string enum: - year - monthYear - date description: >- DATE type only - controls the stored format: `date` → YYYY-MM-DD, `monthYear` → YYYY-MM, `year` → YYYY. Forced to `date` for non-date types. example: date usage_count: type: integer description: >- Read-only. Number of cards referencing this field. Renames + type changes + deletes are blocked while > 0. example: 3 cards_using: type: array items: type: string description: Read-only. The referencing card ids. example: - crd_sophcrprtvpmmnwxah2lomnkee created_at: type: integer description: Unix seconds. example: 1750000000 updated_at: type: integer description: Unix seconds. example: 1750000000 number_format: type: - string - 'null' enum: - integer - decimal - null description: >- `number` fields only: `integer` rejects fractional input; `decimal` (default) allows it. Null on other types. Error: type: object required: - error properties: error: type: object required: - type - code - message properties: type: type: string enum: - invalid_request_error - authentication_error - permission_error - not_found_error - rate_limit_error - idempotency_error - api_error code: type: string message: type: string retry_after: type: integer description: >- Seconds to wait before retrying. Present on rate-limit (429) and idempotency-key-in-use (409) errors; mirrors the `Retry-After` HTTP header. Absent on error types that carry no retry guidance. example: 5 param: type: - string - 'null' request_id: type: string doc_url: type: string format: uri field_errors: type: array description: >- Per-field errors on a 422. At most 100 entries: a request with more errors gets the first 100. items: type: object properties: param: type: string code: type: string message: type: string expected_currency: type: string description: >- On `currency_mismatch`: the business currency the request must use. Absent on every other field error. description: >- The error payload: type (category), code (machine-readable), message (human-readable), retry_after (seconds, on rate-limit/idempotency-in-use errors only), param (offending field), request_id, doc_url, field_errors[]. description: >- Standard error envelope. Branch on `error.code`; include `error.request_id` in support requests. See the Errors guide. securitySchemes: apiKey: type: http scheme: bearer description: >- Your secret API key as a Bearer token: `Authorization: Bearer vxn_sk_...`. Keys are created and scoped in the dashboard - see [Authentication](/api-reference/introduction#authentication). ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.