If you know the name of the VM then you can find it, including its id,
doing a search:

https://engine.example.com/ovirt-engine/api/vms?search=name%3Dmyvm 

If you prefer to use a script, which is probably the right thing, then
you can do something like this, using the Python SDK:

---8<---
#!/usr/bin/python

from ovirtsdk.api import API
from ovirtsdk.xml import params

# Connect to the server:
api = API(
    url="https://engine.example.com/ovirt-engine/api",
    username="admin@internal",
    password="******",
    ca_file="/etc/pki/ovirt-engine/ca.pem",
    debug=False
)

# Find the VM:
vm = api.vms.get(name="myvm")

# Print the id:
print(vm.get_id())

# Disconnect:
api.disconnect()
--->8---

Once you have the VM you can create a snapshot like this:

---8<---
vm.snapshots.add(
    params.Snapshot(description="My snapshot")
)
--->8---

You can also use the Java SDK, if you prefer Java.

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