Getting Started

API Fundamentals

URI

The Mobile Money API uses the following URI format:

{…]/{version}/mm/{Resource}

Where:

• … is defined upon implementation of the API by the API provider.

• version is as per standards defined in the API Versioning section.

• mm is literal for ‘Mobile Money’.

• resource identifies the object and resource that is the subject of the API.

Methods

The specification supports the following request methods:

• POST. Used to create a resource 

• PATCH. Used to update a resource

• GET. Used to return a representation of a resource or a collection of resources.

Patch Specifics

Updates to resources are accomplished by use of the HTTP PATCH method. The PATCH format is based upon IETF RFC 6902.  The replace operation replaces the value of the target property with the supplied value. An example of a replace operation is [{ "op": "replace", "path": "/XYZ", "value": “test” }] where XYZ is the target property.

Resource Naming

The resource part of the URI path identifies the type of resource and if applicable, the specific resource for which an operation is to be performed. Resources are reflected in plural and by use of nouns, for example, /accounts/bills.

Client Correlation ID

A client correlation id can be supplied by the API client on HTTP POST and PATCH requests. The client correlation id is a UUID that enables the client to correlate the API request with the resource created/updated by the provider. The client correlation id is specified in the HTTP Request Header. When a provider issues a callback, the provider should ensure that the original correlation id provided by the client is placed in request header.

The client correlation ID supports safe operations. A POST request that is submitted with a correlation ID that has already been supplied will be rejected as unsafe, thus avoiding transaction duplication.

Use Case Flow Patterns

All use cases supported by the API are built on standardised flow patterns. Flow patterns exist for viewing, updating, and creating resources. 

There are two standard flows:

• Synchronous Flow. The final resource is always provided in response to an API request. There is no interim response. Can be used with POST, PATCH and GET requests.

• Asynchronous Flow. An interim response is always provided in response to an API request in the form of a Request State object. The final response is then provided via a callback or alternatively can be accessed via polling on Request State. Can be used with POST and PATCH requests.  

More detail can be found in the API Behavioural Model section.

Case Sensitivity

All API properties are defined in camelCase format.

All enumeration values referenced within the API use lower case notation – this includes acronyms and abbreviations. The only exceptions are for 

• ISO Codes (country and currency) – the API uses these codes as defined per ISO. 

• Error Codes. Upper Case is used to identify the first letter of each word to assist readability. 

HTTP Header Information

The following header information can be supplied for the mobile money API.

For the security headers, please also refer to the Mobile Money API Security Design for further information.

Standard Request Headers

Standard Response Headers

Custom Request Headers

Header	Value	Optionality	Notes
X-API-Key	Used to pass pre-shared client's API key to the server	Conditional	Only required when API Client Authentication based on API key is used.
X-User-Bearer	Used to pass user’s access token	Conditional	Only required when OAuth 2.0/OIDC authorisation framework is used for end-user authentication.
X-Date	{The date and time that the message was sent in HTTP-date format - RFC 7231}	Conditional	Used for Basic message integrity checks.
X-Client-Id	Used to pass pre-shared client's identifier to the server	Conditional	Can be used in addition to X-API-Key.
X-Content-Hash	SHA-256 hex digest of the request content (encrypted or plain)	Conditional	Applicable only if the HTTP request contains JSON body and basic data integrity checking is to be performed.
X-CorrelationID	UUID	Conditional	Please refer to Client Correlation ID.
X-User-Credential-1	Contains an authentication credential of the end user (e.g. PIN, Password).	Conditional	Should only be used when OAuth 2.0/OIDC authorisation framework has not been implemented by the API Provider.
X-User-Credential-2	Contains an authentication credential of the end user (e.g. PIN, Password). Can be used when a second credential is required.	Conditional	Should only be used when OAuth 2.0/OIDC authorisation framework has not been implemented by the API Provider.
X-Channel	string containing the channel that was used to originate the request. For example, USSD, Web, App..	Conditional	Used to identify the API invocation channel.
X-Callback-URL	string containing the URL which should receive the Callback for asynchronous requests.	Conditional	Will only be used by the API provider if they have implemented the Callback method.

Custom Response Headers

 

API Versioning

When changes are made to the Mobile Money API, a new version is released. There are three types of API versions:

• major (backwards incompatible)

• minor (backwards compatible)

• patch (backwards compatible)

The following types of changes are considered to be backwards compatible:

• Addition of new API Services.

• Adding optional request properties and/or optional input parameters such as query strings to existing objects.

• Addition of new properties to existing API responses.

• Changing the order of properties within a request or response object.

• New error codes.

The following types of changes are considered to be backwards incompatible and hence major:

• Introducing mandatory properties.

• Changing datatypes on properties.

• Changes to API URIs/Paths.

The version that a client intends to use is indicated in the path. Format is ‘X.Y.Z’ where ‘X’ is the major version, ‘Y’ is the minor version and ‘Z’ is a patch version. Versions are sequentially numbered. When a major version is incremented, the minor version is reset to zero. 

The following table provides examples of API version compatibility:

Amount Validation

The mobile money API applies common validation to all amount properties. The following rules are applied during validation:

• Between zero and four decimal places can be supplied.

• Leading zeroes are not permitted except where the value is less than 1. For any value less than one, one and only one leading zero must be supplied.

• Trailing zeroes are permitted.

• Negative values are not permitted.

• Maximum value that can be supplied is 999999999999999999.9999.

Amount validation examples are shown below.

API Behaviour & Error Handling

The Mobile Money API manages API state and exception handling in a harmonised manner:

• API Behavioural Model. Provides standardised flows for synchronous and asynchronous processing patterns.

• API Error Handling. Supports use of standardised HTTP response codes and an errors object that returns additional information as to why the request failed.

• API Heartbeat enables API provider service availability to be established by clients.

The responses object enables clients to request a missing API response.

API Behavioural Model

Overview

API behaviour is governed by the following factors:

• The resource.

• The type of operation, i.e. create, update, or read.

• Whether the provider will process the request synchronously.

• Whether the provider implements callback or polling methods for asynchronous processing.

Request State Object

Asynchronous flows involve a callback mechanism or a polling mechanism to enable the client to determine the final state of the request. Both mechanisms involve the use of the Request State object as per below:      

• Callback. A request is initiated via a HTTP POST or PATCH request with an intermediate response represented by a Request State object. Once the request has been completed, the provider will initiate a PUT request to the URL specified by the client in the X-Callback-URL request header. The callback will provide the client with one of the following:

  • Final representation of the resource for successful creation requests

  • A {"result": "success"} response for successful update requests  

• Polling. A request is initiated via a HTTP POST or PATCH request with an intermediate response provided in the form of the Request State object. A HTTP GET is then issued against /requeststate by the client at intervals until the final resource state and resource reference is returned.

 

The object definition for RequestState is described below.

Generic API Sequence Diagrams

Figures 1 to 7 illustrate the standard flows for the Mobile Money API. The green flows represent a success path and red flows represent a failure path. 

 

Figure 1 : Mobile Money API Generic Sequence Diagram for Read Requests

 

Figure 2 : Mobile Money API Synchronous Diagram for Create Requests

Figure 3 : Mobile Money API Asynchronous Callback Diagram for Create Requests

 

Figure 4 : Mobile Money API Asynchronous Polling Diagram for Create Requests

Figure 5 : Mobile Money API Synchronous Diagram for Update Requests

Figure 6 : Mobile Money API Asynchronous Callback Diagram for Update Requests

 

  Figure 7 : Mobile Money API Asynchronous Polling Diagram for Update Requests

API Error Handling

Summary of HTTP Response Codes

The following HTTP response codes are returned for the listed methods:

*Note that the ‘intermediate’ column in the table above relates to the HTTP response for the first leg of an asynchronous request.

HTTP Error Response Codes

 

Errors Object Definition

The mobile money API uses the errors object to provide error details to API clients. The following properties are included:

• Error Category. All error codes must be associated with an appropriate category. This provides context and uniqueness to the error code.

• Error Code. Provides the reason for the request failure. Error codes are generally granular, i.e. they provide a specific reason for failure. In some cases, granularity is neither possible nor desirable. Where this is the case, a generic code has been defined. Cases include:

  • The API Provider has generated an error that does not map to existing Rule error codes. 

  • The API Provider wishes to avoid disclosure of confidential information regarding the resource or parties to the resource. For example, the fact that a customer has breached their monthly transaction limit may not be disclosed to specific clients.

• Error Description. A textual description of the error code.

• Error Parameters. Provides a construct to communicate supplementary information regarding the error in key/value pairs. The supplementary information is currently non-harmonised and can include:

  • The API provider-specific Error Code and Description.

  • Additional identification of the error subject, e.g. account identifiers, invalid properties etc…

  • Diagnostic information, e.g. affected subsystem, licence failure type etc…

With the errorParameters property, care should be taken regarding confidentially of information. Confidential parameter information should only be disclosed to trusted clients.

Error Parameters Object

Allows error parameter properties to be specified in the form of key/value pairs. The number of key/value pairs is limited to 20.

API Error Codes

 

API Heartbeat

The Heartbeat API is used for monitoring purposes and establishes whether the system of an API provider is in a state that enables a client to submit a request for processing within established SLAs. There are three states that can be returned by the API provider in response to a heartbeat request:

• Available. The system is available and can receive and complete requests within SLAs.

• Degraded. The system can receive and complete requests but not within SLAs, i.e. delay in transaction processing is anticipated. When known, the expected processing delay time can be returned by the provider.

• Unavailable. The system cannot receive and process requests. Any submitted requests will fail whilst the system is in this state.

The Heartbeat can be requested using the following path:

• GET /heartbeat 

Only synchronous API Heartbeat requests are supported. The HTTP response contains the following properties.

Missing Response Retrieval

In some circumstances, the client may not have received the final representation of the resource for which it attempted to create. For example, a proxy server issue may have resulted in a HTTP 5xx response but the provider may have actually successfully completed the request. The /responses API allows a client to identify and retrieve the final representation of the resource assuming that the resource was created. In order to get a representation, the client issues a GET /Responses/{clientCorrelationId}. The provider will then match the client correlation id to the appropriate resource and return a link to that resource. If the resource is not found for the given correlation id then a HTTP 404 will be returned. 

The response object for /responses is detailed below.