it depends on which library are you using as RPC Client how it's implemented extra args and kwargs
for python, it's work like

models = xmlrpc.client.ServerProxy('http://localhost:8069/xmlrpc/2/object')
res = models.execute_kw(db, uid, password, 'res.partner', 'search', [[]], {'limit':5, 'offset': 5})​

so maybe it's should be like 
"args": [
         "odoo_db", "2", "a", "res.partner", "search",  [[]], {'limit':5, 'offset': 5})​
],​

How can I put a range in this same query you describe?