diff --git a/src/google/adk/tools/openapi_tool/openapi_spec_parser/openapi_spec_parser.py b/src/google/adk/tools/openapi_tool/openapi_spec_parser/openapi_spec_parser.py
index 2e0e543fa3..1745698e41 100644
--- a/src/google/adk/tools/openapi_tool/openapi_spec_parser/openapi_spec_parser.py
+++ b/src/google/adk/tools/openapi_tool/openapi_spec_parser/openapi_spec_parser.py
@@ -205,10 +205,21 @@ def _collect_operations(
         if operation_dict is None:
           continue
 
-        # Append path-level parameters
-        operation_dict["parameters"] = operation_dict.get(
-            "parameters", []
-        ) + path_item.get("parameters", [])
+        # Append path-level parameters. An operation-level parameter with the
+        # same name and location overrides the path-level one, so appending
+        # both would ask the model for the same value twice.
+        operation_parameters = operation_dict.get("parameters", [])
+        overridden = {
+            (parameter["name"], parameter.get("in"))
+            for parameter in operation_parameters
+            if isinstance(parameter, dict) and "name" in parameter
+        }
+        operation_dict["parameters"] = operation_parameters + [
+            parameter
+            for parameter in path_item.get("parameters", [])
+            if not isinstance(parameter, dict)
+            or (parameter.get("name"), parameter.get("in")) not in overridden
+        ]
 
         # If operation ID is missing, assign an operation id based on path
         # and method
diff --git a/src/google/adk/tools/openapi_tool/openapi_spec_parser/operation_parser.py b/src/google/adk/tools/openapi_tool/openapi_spec_parser/operation_parser.py
index 36a2b19402..12214ac313 100644
--- a/src/google/adk/tools/openapi_tool/openapi_spec_parser/operation_parser.py
+++ b/src/google/adk/tools/openapi_tool/openapi_spec_parser/operation_parser.py
@@ -25,6 +25,7 @@
 from fastapi.encoders import jsonable_encoder
 from fastapi.openapi.models import Operation
 from fastapi.openapi.models import Parameter
+from fastapi.openapi.models import ParameterInType
 from fastapi.openapi.models import Reference
 from fastapi.openapi.models import RequestBody
 from fastapi.openapi.models import Response
@@ -139,8 +140,11 @@ def _process_operation_parameters(self) -> None:
       )
       if not schema.description:
         schema.description = description
-      # param.required can be None
-      required = param.required if param.required is not None else False
+      # OpenAPI requires `required: true` on every path parameter, and the URL
+      # cannot be built without one, so treat it as required even when the
+      # spec (e.g. an operation-level override) leaves the flag out.
+      # param.required can be None.
+      required = param.in_ == ParameterInType.path or bool(param.required)
 
       self._params.append(
           ApiParameter(
diff --git a/tests/unittests/tools/openapi_tool/openapi_spec_parser/test_openapi_spec_parser.py b/tests/unittests/tools/openapi_tool/openapi_spec_parser/test_openapi_spec_parser.py
index e5bff337ce..587c41f872 100644
--- a/tests/unittests/tools/openapi_tool/openapi_spec_parser/test_openapi_spec_parser.py
+++ b/tests/unittests/tools/openapi_tool/openapi_spec_parser/test_openapi_spec_parser.py
@@ -685,6 +685,100 @@ def test_parse_spec_with_path_level_parameters(openapi_spec_generator):
   assert local_param.type_value is int
 
 
+def test_parse_spec_operation_parameter_overrides_path_level_parameter(
+    openapi_spec_generator,
+):
+  """A same-named operation parameter replaces the path-level one."""
+  openapi_spec = {
+      "openapi": "3.1.0",
+      "info": {"title": "Accounts API", "version": "1.0.0"},
+      "paths": {
+          "/accounts/{accountId}": {
+              "parameters": [
+                  {
+                      "name": "accountId",
+                      "in": "path",
+                      "required": True,
+                      "schema": {"type": "string"},
+                      "description": "Shared account id",
+                  },
+                  # Same name, different location: not overridden.
+                  {
+                      "name": "accountId",
+                      "in": "header",
+                      "schema": {"type": "string"},
+                  },
+              ],
+              "get": {
+                  "operationId": "getAccount",
+                  "parameters": [{
+                      "name": "accountId",
+                      "in": "path",
+                      "required": True,
+                      "schema": {"type": "string"},
+                      "description": "Account id, e.g. ACC-123",
+                  }],
+                  "responses": {"200": {"description": "ok"}},
+              },
+          }
+      },
+  }
+
+  operation = openapi_spec_generator.parse(openapi_spec)[0]
+
+  assert [
+      (p.original_name, p.param_location) for p in operation.parameters
+  ] == [
+      ("accountId", "path"),
+      ("accountId", "header"),
+  ]
+  assert operation.parameters[0].description == "Account id, e.g. ACC-123"
+
+
+def test_parse_spec_path_parameter_is_required_even_when_override_omits_it(
+    openapi_spec_generator,
+):
+  """An override that leaves out `required` must not make a path param optional."""
+  openapi_spec = {
+      "openapi": "3.1.0",
+      "info": {"title": "Accounts API", "version": "1.0.0"},
+      "paths": {
+          "/accounts/{accountId}": {
+              "parameters": [{
+                  "name": "accountId",
+                  "in": "path",
+                  "required": True,
+                  "schema": {"type": "string"},
+              }],
+              "get": {
+                  "operationId": "getAccount",
+                  "parameters": [
+                      {
+                          "name": "accountId",
+                          "in": "path",
+                          "schema": {"type": "string"},
+                      },
+                      # Non-path parameters keep the operation's own flag.
+                      {
+                          "name": "expand",
+                          "in": "query",
+                          "schema": {"type": "string"},
+                      },
+                  ],
+                  "responses": {"200": {"description": "ok"}},
+              },
+          }
+      },
+  }
+
+  operation = openapi_spec_generator.parse(openapi_spec)[0]
+
+  assert {p.original_name: p.required for p in operation.parameters} == {
+      "accountId": True,
+      "expand": False,
+  }
+
+
 def test_parse_spec_with_invalid_type_any(openapi_spec_generator):
   """Test that schemas with type='Any' are sanitized for Pydantic 2.11+.