How to add nodes in bulk using RestAPI?

I don't think you can do create multiple nodes from the iControl REST API within a single request but you could script it using something like Python and the F5-SDK or with the use of Ansible.

Example Ansible playbook below, you would need to have the F5 device listed in the Ansible

hosts

f5

---
- name: Run tasks on Active LTM
  hosts: f5
  connection: local
  gather_facts: True

  vars:
    f5Provider:
      server: "{{inventory_hostname}}"
      server_port: 443
      user: admin
      password: admin
      validate_certs: no
      transport: rest
    nodelist:
      - {name: 'test01', address: '10.0.0.1'}
      - {name: 'test02', address: '10.0.0.2'}
      - {name: 'test03', address: '10.0.0.3'}
      - {name: 'test04', address: '10.0.0.4'}

  tasks:
    - name: Add nodes
      bigip_node:
        provider: "{{f5Provider}}"
        partition: test
        address: "{{ item.address }}"
        name: "{{ item.name }}"
      loop: "{{nodelist}}"
      delegate_to: localhost
      notify: Save configuration

  handlers:
    - name: Save configuration
      bigip_config:
        save: yes
      delegate_to: localhost

NOTE: this is create four nodes in the

test