# Additional optional APIs

Optionally, IPSOs, PSPs and FXPs may use the following APIs to update the reference data. As these updates may be infrequent, Participants may opt to use the Nexus Service Desk instead. The detailed specifications of these APIs will be included in a later stage.

| API           | Type            | Used when                                                                                        | Used by      | M/RC/O      | Availability                                             |
| ------------- | --------------- | ------------------------------------------------------------------------------------------------ | ------------ | ----------- | -------------------------------------------------------- |
| countries     | PUT             | <p>Updating country specific data, such as:<br>- Value limit<br>- Mandatory message elements</p> | IPSO         | Optional    | Via Nexus Service Desk and as API at launch              |
| countries     | PUT             | Adding new address types, updating the input parameters of existing address types                | PDO via IPSO | Optional    | Via Nexus Service Desk and as API at launch              |
| countries     | PUT             | Updating available currencies for an IPSO                                                        | IPSO         | Optional    | Via Nexus Service Desk only, API not available at launch |
| fee-formulas  | PUT             | Updating country specific D-PSP fee                                                              | IPSO         | Optional    | Via Nexus Service Desk only, API not available at launch |
| fin-insts     | POST/PUT        | Adding/updating a Financial Institution                                                          | IPSO         | Recommended | Via Nexus Service Desk and as API at launch              |
| rates         | POST            | Add/update a live FX rate                                                                        | FXP          | Mandatory   | Only via API                                             |
| relationships | POST/PUT        | Add/update the FXP-PSP relationship, including PSP-based improvements                            | FXP          | Optional    | Via Nexus Service Desk only, API not available at launch |
| tiers         | POST/PUT/DELETE | Create/Update/Delete a tier for a given FXP and source currency                                  | FXP          | Recommended | Via Nexus Service Desk and as API at launch              |


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