---
updatedAt: 2026-08-04T14:08:40.000Z
agentTools:
  projectIndex: https://docs.mesh.complyadvantage.com/llms.txt
---

# Create a new custom field

When you submit a custom field to us, an internal identifier will be assigned. This API allows you to create a custom field for your account.

# OpenAPI definition

```json
{
  "components": {
    "schemas": {
      "activity_CreateCustomFieldRequest": {
        "properties": {
          "data_type": {
            "$ref": "#/components/schemas/activity_CustomFieldDataTypeV3"
          },
          "description": {
            "maxLength": 1000,
            "minLength": 0,
            "type": "string"
          },
          "display_name": {
            "maxLength": 50,
            "minLength": 0,
            "type": "string"
          },
          "key": {
            "maxLength": 50,
            "minLength": 0,
            "pattern": "^[a-z0-9_]+$",
            "type": "string"
          }
        },
        "required": [
          "data_type",
          "description",
          "display_name",
          "key"
        ],
        "type": "object"
      },
      "activity_CustomField": {
        "properties": {
          "data_type": {
            "$ref": "#/components/schemas/activity_CustomFieldDataTypeV3"
          },
          "description": {
            "type": "string"
          },
          "display_name": {
            "type": "string"
          },
          "identifier": {
            "format": "uuid",
            "type": "string"
          },
          "key": {
            "type": "string"
          }
        },
        "required": [
          "data_type",
          "description",
          "display_name",
          "identifier",
          "key"
        ],
        "type": "object"
      },
      "activity_CustomFieldDataTypeV3": {
        "description": "The type of data stored in a custom field.",
        "enum": [
          "TEXT",
          "DECIMAL"
        ],
        "type": "string"
      },
      "activity_ProblemDetailErrorResponse": {
        "additionalProperties": true,
        "properties": {
          "detail": {
            "nullable": true,
            "type": "string"
          },
          "identifier": {
            "format": "uuid",
            "type": "string"
          },
          "instance": {
            "format": "uri",
            "nullable": true,
            "type": "string"
          },
          "status": {
            "format": "int32",
            "nullable": true,
            "type": "integer"
          },
          "timestamp": {
            "format": "date-time",
            "type": "string"
          },
          "title": {
            "nullable": true,
            "type": "string"
          },
          "type": {
            "format": "uri",
            "nullable": true,
            "type": "string"
          }
        },
        "required": [
          "identifier",
          "timestamp"
        ],
        "type": "object"
      }
    },
    "securitySchemes": {
      "BearerAuth": {
        "description": "HTTP Bearer Token Authentication",
        "scheme": "bearer",
        "type": "http"
      }
    }
  },
  "info": {
    "title": "Mesh API",
    "version": "v2.0"
  },
  "openapi": "3.0.3",
  "paths": {
    "/v3/transactions/custom-fields": {
      "post": {
        "description": "When you submit a custom field to us, an internal identifier will be assigned. This API allows you to create a custom field for your account.",
        "operationId": "activityStoreCreateCustomField",
        "requestBody": {
          "content": {
            "application/json": {
              "schema": {
                "$ref": "#/components/schemas/activity_CreateCustomFieldRequest"
              }
            }
          },
          "required": true
        },
        "responses": {
          "201": {
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/activity_CustomField"
                }
              }
            },
            "description": "Custom field created"
          },
          "400": {
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/activity_ProblemDetailErrorResponse"
                }
              }
            },
            "description": "Invalid request"
          },
          "500": {
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/activity_ProblemDetailErrorResponse"
                }
              }
            },
            "description": "Internal Server Error"
          }
        },
        "summary": "Create a new custom field",
        "tags": [
          "Transactions"
        ]
      }
    }
  },
  "security": [
    {
      "BearerAuth": []
    }
  ],
  "servers": [
    {
      "description": "ComplyAdvantage Mesh API",
      "url": "https://api.mesh.complyadvantage.com"
    }
  ],
  "tags": [
    {
      "name": "Transactions"
    }
  ]
}
```