diff --git a/configs/agents/billing.yaml b/configs/agents/billing.yaml
index 1e2d44d..2b4cc3a 100644
--- a/configs/agents/billing.yaml
+++ b/configs/agents/billing.yaml
@@ -11,7 +11,7 @@ system_prompt: |
    When the customer asks a question:
 
    1. ALWAYS use the provided tools to retrieve accurate customer billing data:
-      - get_billing_info: Use this tool to get detailed billing statements based on customer, billing_start_date and billing_end_date. The value of customer should always be present and provided by the user. Filter the results if the user provides values for additional_charges, total_amount, and payment status. Use the default values if the user does not provide values for these parameters.
+      - get_billing_info: Use this tool to get detailed billing statements based on customer, billing_start_date and billing_end_date. The customer ID is always available. Filter the results if the user provides values for additional_charges, total_amount, and payment status. Use the default values if the user does not provide values for these parameters.      
       - get_usage_info: Use this tool to get usage details including data, voice, and SMS usage for a specific time period.
       - system.ai.python_exec: Use this tool to execute python code to get the current date and month and generate the values for usage_start_date, usage_end_date, billing_start_date and billing_end_date based on the current date and month and the timeframe user asks for.
 
diff --git a/telco_support_agent/agents/base_agent.py b/telco_support_agent/agents/base_agent.py
index d851b87..1f7a912 100644
--- a/telco_support_agent/agents/base_agent.py
+++ b/telco_support_agent/agents/base_agent.py
@@ -413,8 +413,45 @@ def execute_tool(self, tool_name: str, args: dict) -> Any:
                     result = self.vector_search_tools[tool_name].execute(**args)
                 else:
                     uc_function_name = tool_name.replace("__", ".")
+                    # Convert None values and string null representations to SQL NULL by omitting them
+                    cleaned_args = {}
+                    for k, v in args.items():
+                        # Skip None values and string representations of null/empty
+                        if v is None:
+                            continue
+                        if isinstance(v, str) and v.lower() in ("null", "none", ""):
+                            continue
+
+                        # Convert numeric values appropriately for UC functions
+                        if isinstance(v, int | float):
+                            # For parameters that should be DOUBLE, always use float
+                            if k.endswith(("_input", "_amount", "_charge", "_value")):
+                                cleaned_args[k] = float(v)
+                            else:
+                                cleaned_args[k] = v
+                        elif (
+                            isinstance(v, str)
+                            and v.replace(".", "").replace("-", "").isdigit()
+                        ):
+                            try:
+                                # For DOUBLE parameters, always convert to float
+                                if k.endswith(
+                                    ("_input", "_amount", "_charge", "_value")
+                                ):
+                                    cleaned_args[k] = float(v)
+                                else:
+                                    cleaned_args[k] = float(v) if "." in v else int(v)
+                            except ValueError:
+                                cleaned_args[k] = (
+                                    v  # Keep as string if conversion fails
+                                )
+                        else:
+                            cleaned_args[k] = v
+                    logger.debug(
+                        f"UC function {uc_function_name}: original args {args}, cleaned args {cleaned_args}"
+                    )
                     result = self.uc_client.execute_function(
-                        function_name=uc_function_name, parameters=args
+                        function_name=uc_function_name, parameters=cleaned_args
                     ).value
 
                 span.set_outputs(result)
diff --git a/telco_support_agent/tools/billing/functions.py b/telco_support_agent/tools/billing/functions.py
index 8c4ecae..451abe8 100644
--- a/telco_support_agent/tools/billing/functions.py
+++ b/telco_support_agent/tools/billing/functions.py
@@ -23,9 +23,9 @@ def register_get_billing_info(uc_config: UCConfig):
           customer STRING COMMENT 'The customer ID in the format CUS-XXXXX',
           billing_start_date_input STRING COMMENT 'The billing start date in YYYY-MM-DD format. Defaults to first day of current month.',
           billing_end_date_input STRING COMMENT 'The billing end date in YYYY-MM-DD format. Defaults to first day of next month.',
-          additional_charges_input DOUBLE COMMENT 'Filter on additional_charges. Must be non negative. If 0, only rows with non-NULL additional_charges are included. Can be NULL to skip filtering.',
-          total_amount_input DOUBLE COMMENT 'Filter on total_amount. Must be non negative. If 0, only rows with non-NULL total_amount are included. Can be NULL to skip filtering.',
-          status_input STRING COMMENT 'Billing status. Possible values: Paid, Unpaid, Late, Partial, All. Defaults to All. If All, return rows of all statuses.'
+          additional_charges_input DOUBLE DEFAULT NULL COMMENT 'Filter on additional_charges. Must be non negative. If 0, only rows with non-NULL additional_charges are included. Can be NULL to skip filtering.',
+          total_amount_input DOUBLE DEFAULT NULL COMMENT 'Filter on total_amount. Must be non negative. If 0, only rows with non-NULL total_amount are included. Can be NULL to skip filtering.',
+          status_input STRING DEFAULT 'All' COMMENT 'Billing status. Possible values: Paid, Unpaid, Late, Partial, All. Defaults to All. If All, return rows of all statuses.'
         )
         RETURNS STRING
         COMMENT 'Retrieves all columns of the billing table for all rows for a customer within the specified date range, with optional filters for additional_charges, total_amount, and status. Example usage: SELECT {function_name}("CUS-10601","2025-06-01","2025-06-01",NULL,NULL,"Paid")'