FieldSpec

Describes a single field within the file

namestringrequired

Internal field identifier (snake_case recommended)

Example: account_number

displayNamestring

Human-readable label (defaults to name)

Example: Account Number

typeFieldType (string)required

Data type for a field

Possible values: [STRING, INTEGER, LONG, DECIMAL, AMOUNT, DATE, DATETIME, BOOLEAN, ALPHANUMERIC, ROUTING_NUMBER, ACCOUNT_NUMBER, ABA, ENUM]

Example: AMOUNT

startPositioninteger

1-based character start position (fixed-width only)

Example: 1

lengthinteger

Field length in characters (fixed-width only)

Example: 17

columnIndexinteger

0-based column index (CSV/delimited without header)

Example: 0

columnNamestring

Column header name (CSV/delimited with hasHeader: true)

Example: ACCT_NO

pathstring

XPath (XML) or JSONPath (JSON) expression

Example: $.payment.accountNumber

xmlAttributestring

XML attribute name (XML only)

requiredboolean

Whether the field must be present

Default value: true

nullableboolean

Whether an empty/null value is acceptable

Default value: false

defaultValuestring

Value to use when field is absent or null

formatstring

Date/number format pattern (e.g. yyyyMMdd, #,##0.00)

Example: yyyyMMdd

scaleinteger

Decimal places for AMOUNT/DECIMAL fields

Example: 2

validationRegexstring

Regular expression the field value must match

Example: ^[0-9]{9}$

minLengthinteger

Minimum string length

maxLengthinteger

Maximum string length

Example: 17

allowedValuesstring[]

Whitelist of accepted values

sensitiveboolean

PII flag — value will be masked in logs and traces

Default value: false

descriptionstring

Optional documentation for this field

FieldSpec

{
  "name": "account_number",
  "displayName": "Account Number",
  "type": "AMOUNT",
  "startPosition": 1,
  "length": 17,
  "columnIndex": 0,
  "columnName": "ACCT_NO",
  "path": "$.payment.accountNumber",
  "xmlAttribute": "string",
  "required": true,
  "nullable": false,
  "defaultValue": "string",
  "format": "yyyyMMdd",
  "scale": 2,
  "validationRegex": "^[0-9]{9}$",
  "minLength": 0,
  "maxLength": 17,
  "allowedValues": [
    "string"
  ],
  "sensitive": false,
  "description": "string"
}