> For AI agents: the complete documentation index is available at /llms.txt, the full documentation bundle is available at /llms-full.txt. # Start a transaction **Method:** `PUT` **Path:** `/api/transaction/{transactionId}/start` Start the signing process for a transaction. All required files and signers must be configured before starting. Once started, the transaction cannot be modified and signers will be notified to begin signing. ## Parameters | Name | In | Type | Required | Description | | ----------------- | ---- | ------ | -------- | ---------------------------------- | | **transactionId** | path | string | Yes |

The transaction ID to start

| ## Responses ### 204 Transaction started successfully ### 400 The transaction could not be started. This typically occurs if the transaction contains errors or is in a Failed status. Content-Type: `application/json` **Schema:** [ErrorResponse](/openapi/models/ErrorResponse.md) #### Properties | Name | Type | Description | | ------------ | ------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | **type** | String |

A URI reference identifying the problem type. This property is always present in RFC 7807 responses.

| | **title** | String |

A short, human-readable summary of the problem

| | **detail** | String |

A human-readable explanation specific to this occurrence of the problem

| | **status** | Integer |

The HTTP status code

| | **instance** | String |

A URI reference that identifies the specific occurrence of the problem

| | **Message** | String |

Deprecated (Legacy Format Only): Contains the error message in the old response format. This property appears alone in legacy error responses and is mutually exclusive with the RFC 7807 properties above. Will be phased out as we complete our transition to RFC 7807.

| ### 401 Unauthorized - user not creator of transaction Content-Type: `application/json` **Schema:** [ErrorResponse](/openapi/models/ErrorResponse.md) #### Properties | Name | Type | Description | | ------------ | ------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | **type** | String |

A URI reference identifying the problem type. This property is always present in RFC 7807 responses.

| | **title** | String |

A short, human-readable summary of the problem

| | **detail** | String |

A human-readable explanation specific to this occurrence of the problem

| | **status** | Integer |

The HTTP status code

| | **instance** | String |

A URI reference that identifies the specific occurrence of the problem

| | **Message** | String |

Deprecated (Legacy Format Only): Contains the error message in the old response format. This property appears alone in legacy error responses and is mutually exclusive with the RFC 7807 properties above. Will be phased out as we complete our transition to RFC 7807.

| ### 403 Forbidden - authorization policy violation Content-Type: `application/json` **Schema:** [ErrorResponse](/openapi/models/ErrorResponse.md) #### Properties | Name | Type | Description | | ------------ | ------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | **type** | String |

A URI reference identifying the problem type. This property is always present in RFC 7807 responses.

| | **title** | String |

A short, human-readable summary of the problem

| | **detail** | String |

A human-readable explanation specific to this occurrence of the problem

| | **status** | Integer |

The HTTP status code

| | **instance** | String |

A URI reference that identifies the specific occurrence of the problem

| | **Message** | String |

Deprecated (Legacy Format Only): Contains the error message in the old response format. This property appears alone in legacy error responses and is mutually exclusive with the RFC 7807 properties above. Will be phased out as we complete our transition to RFC 7807.

| ### 500 Internal server error Content-Type: `application/json` **Schema:** [ErrorResponse](/openapi/models/ErrorResponse.md) #### Properties | Name | Type | Description | | ------------ | ------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | **type** | String |

A URI reference identifying the problem type. This property is always present in RFC 7807 responses.

| | **title** | String |

A short, human-readable summary of the problem

| | **detail** | String |

A human-readable explanation specific to this occurrence of the problem

| | **status** | Integer |

The HTTP status code

| | **instance** | String |

A URI reference that identifies the specific occurrence of the problem

| | **Message** | String |

Deprecated (Legacy Format Only): Contains the error message in the old response format. This property appears alone in legacy error responses and is mutually exclusive with the RFC 7807 properties above. Will be phased out as we complete our transition to RFC 7807.

|