diff --git a/python/packages/core/agent_framework/_tools.py b/python/packages/core/agent_framework/_tools.py
index c78267d34ac..ea6886e7768 100644
--- a/python/packages/core/agent_framework/_tools.py
+++ b/python/packages/core/agent_framework/_tools.py
@@ -1599,7 +1599,11 @@ def _matches_json_schema_type(value: Any, schema_type: str) -> bool:
         case "string":
             return isinstance(value, str)
         case "integer":
-            return isinstance(value, int) and not isinstance(value, bool)
+            # JSON Schema "integer" is a number without a fraction, so 3.0
+            # is valid (#9843). bool is not an integer here.
+            return (isinstance(value, int) and not isinstance(value, bool)) or (
+                isinstance(value, float) and value.is_integer()
+            )
         case "number":
             return (isinstance(value, int | float)) and not isinstance(value, bool)
         case "boolean":
@@ -1614,6 +1618,21 @@ def _matches_json_schema_type(value: Any, schema_type: str) -> bool:
             return True
 
 
+def _normalize_json_schema_value(value: Any, allowed_types: list[str]) -> Any:
+    """Coerce a value to the type the schema asked for, where JSON is looser.
+
+    JSON has a single number type, so a model sends ``3.0`` for a parameter the
+    schema declares as ``integer``. Accepting it is only half the fix: a tool that
+    runs ``range(count)`` or indexes with it still raises on a float. Whole-number
+    floats become ``int`` when ``integer`` is the only numeric type allowed. When
+    ``number`` is allowed too the value's own type is the answer, so nothing is
+    narrowed to fit a declaration that also permits fractions.
+    """
+    if isinstance(value, float) and value.is_integer() and "integer" in allowed_types and "number" not in allowed_types:
+        return int(value)
+    return value
+
+
 def _validate_arguments_against_schema(
     *,
     arguments: Mapping[str, Any],
@@ -1634,7 +1653,7 @@ def _validate_arguments_against_schema(
         if unexpected_fields:
             raise TypeError(f"Unexpected argument(s) for '{tool_name}': {', '.join(unexpected_fields)}")
 
-    for field_name, field_value in parsed_arguments.items():
+    for field_name, field_value in list(parsed_arguments.items()):
         if not isinstance(properties.get(field_name), dict):
             continue
 
@@ -1649,6 +1668,7 @@ def _validate_arguments_against_schema(
                     f"Invalid type for '{field_name}' in '{tool_name}': "
                     f"expected {schema_type}, got {type(field_value).__name__}"
                 )
+            parsed_arguments[field_name] = _normalize_json_schema_value(field_value, [schema_type])
             continue
 
         if isinstance(schema_type, list):
@@ -1658,6 +1678,7 @@ def _validate_arguments_against_schema(
                     f"Invalid type for '{field_name}' in '{tool_name}': expected one of "
                     f"{allowed_types}, got {type(field_value).__name__}"
                 )
+            parsed_arguments[field_name] = _normalize_json_schema_value(field_value, allowed_types)
 
     return parsed_arguments
 
diff --git a/python/packages/core/tests/core/test_tools.py b/python/packages/core/tests/core/test_tools.py
index d7db2db4971..68030a53efb 100644
--- a/python/packages/core/tests/core/test_tools.py
+++ b/python/packages/core/tests/core/test_tools.py
@@ -593,6 +593,79 @@ def search(query: str, max_results: int = 10) -> str:
         await search.invoke(arguments={"query": "hello", "max_results": "three"})
 
 
+async def test_tool_json_schema_integer_accepts_whole_number_float():
+    """JSON Schema "integer" accepts whole-number floats like 3.0 (#9843)."""
+
+    json_schema = {
+        "type": "object",
+        "properties": {
+            "count": {"type": "integer"},
+        },
+        "required": ["count"],
+    }
+    received: list[Any] = []
+
+    @tool(name="counter", description="Count tool", schema=json_schema)
+    def counter(count: int) -> str:
+        received.append(count)
+        return str(count)
+
+    # 3.0 is a valid JSON Schema integer; it reaches the callable as the integer
+    # the schema asked for, so range(count) and friends work on it.
+    await counter.invoke(arguments={"count": 3.0})
+    assert received == [3]
+    assert isinstance(received[0], int)
+
+    # 3.5 is not a valid integer.
+    with pytest.raises(TypeError, match="Invalid type for 'count'"):
+        await counter.invoke(arguments={"count": 3.5})
+
+
+async def test_tool_json_schema_nullable_integer_normalizes_whole_number_float():
+    """A nullable integer schema accepts 3.0 and still hands the callable an int."""
+
+    json_schema = {
+        "type": "object",
+        "properties": {
+            "count": {"type": ["integer", "null"]},
+        },
+    }
+    received: list[Any] = []
+
+    @tool(name="counter", description="Count tool", schema=json_schema)
+    def counter(count: int | None) -> str:
+        received.append(count)
+        return str(count)
+
+    await counter.invoke(arguments={"count": 3.0})
+    assert received == [3]
+    assert isinstance(received[0], int)
+
+    await counter.invoke(arguments={"count": None})
+    assert received == [3, None]
+
+
+async def test_tool_json_schema_number_alongside_integer_keeps_the_float():
+    """When the schema also allows "number", the value's own type is the answer."""
+
+    json_schema = {
+        "type": "object",
+        "properties": {
+            "value": {"type": ["integer", "number"]},
+        },
+    }
+    received: list[Any] = []
+
+    @tool(name="measure", description="Measure tool", schema=json_schema)
+    def measure(value: float) -> str:
+        received.append(value)
+        return str(value)
+
+    await measure.invoke(arguments={"value": 3.0})
+    assert received == [3.0]
+    assert isinstance(received[0], float)
+
+
 def test_tool_decorator_with_json_schema_preserves_custom_properties():
     """Test schema passthrough keeps custom JSON schema properties."""