A commit script in Junos is used to enforce policies and configuration constraints on the device. These scripts are written in Extensible Stylesheet Language Transformations (XSLT) or Python and are executed automatically during the commit process of a configuration change.
In this context, to prevent the deletion of the SNMP configuration, a commit script is the appropriate choice.
It can be designed to check the configuration changes being committed and reject any commit that attempts to delete or modify the SNMP configuration. This script essentially acts as a gatekeeper, ensuring that only allowable changes are committed to the device configuration.
Supporting References:
* Juniper Networks Commit Scripts Documentation:The official Juniper documentation provides examples and use cases of commit scripts, including how they can be used to prevent unauthorized changes to the device configuration.
* "Junos Automation Scripting"by Jonathan Looney: This resource gives practical examples and best practices for creating commit scripts to enforce configuration policies in Junos OS.

In Junos, theJET (Junos Extension Toolkit)API supports direct modification of theEphemeral database.
The Ephemeral database is a temporary configuration database used in Junos OS, allowing for changes that do not persist after a reboot unless explicitly committed to the permanent configuration.
* JET API: Allows for high-performance interactions with Junos, including the ability to make changes to the Ephemeral database, which is useful for temporary configurations, dynamic policies, and other operational tasks.
Other options like WebSocket, SOAP, and REST do not provide direct access to the Ephemeral database in Junos.
* Juniper Networks JET Documentation: Details how JET API interacts with the Ephemeral database.
* Junos Automation and DevOps Documentation: Discusses the use of JET for automation and dynamic configuration.
References:

https://www.w3schools.com/xml/xpath_syntax.asp