diff --git a/openhcs/mcp/server.py b/openhcs/mcp/server.py
index 7b6670dde..90a44d50e 100644
--- a/openhcs/mcp/server.py
+++ b/openhcs/mcp/server.py
@@ -34,6 +34,7 @@
 from metaclass_registry import AutoRegisterMeta
 from pydantic import Field as PydanticField
 from pydantic import WithJsonSchema
+from python_introspect import dataclass_from_mapping
 from zmqruntime.config import TransportMode
 
 from openhcs.agent.authoring_contexts import AuthoringContextDeclaration
@@ -1977,31 +1978,7 @@ def connection_parameters(
         cls,
         timeout_policy: type[McpControlTimeoutPolicy] = McpViewerTimeoutPolicy,
     ) -> tuple[Parameter, ...]:
-        return (
-            Parameter(
-                "port",
-                Parameter.KEYWORD_ONLY,
-                annotation=int,
-            ),
-            Parameter(
-                "host",
-                Parameter.KEYWORD_ONLY,
-                default="localhost",
-                annotation=str,
-            ),
-            Parameter(
-                "transport_mode",
-                Parameter.KEYWORD_ONLY,
-                default=None,
-                annotation=str | None,
-            ),
-            Parameter(
-                "timeout_ms",
-                Parameter.KEYWORD_ONLY,
-                default=None,
-                annotation=_timeout_parameter_annotation(timeout_policy),
-            ),
-        )
+        return McpViewerConnectionToolFields.signature_parameters(timeout_policy)
 
     @classmethod
     def control_args(
@@ -2009,13 +1986,10 @@ def control_args(
         arguments: Mapping[str, JsonValue],
         timeout_policy: type[McpControlTimeoutPolicy] = McpViewerTimeoutPolicy,
     ) -> "McpViewerConnectionToolArgs":
-        return McpViewerConnectionToolArgs.from_fields(
-            port=arguments["port"],
-            host=arguments["host"],
-            transport_mode=arguments["transport_mode"],
-            timeout_ms=arguments["timeout_ms"],
-            timeout_policy=timeout_policy,
-        )
+        return dataclass_from_mapping(
+            McpViewerConnectionToolFields,
+            arguments,
+        ).to_control_args(timeout_policy)
 
     @staticmethod
     def option_parameters(
@@ -2664,14 +2638,32 @@ def _json_object_or_empty(value: dict | None) -> dict:
     return dict(value)
 
 
-@dataclass(frozen=True, slots=True)
+@dataclass(frozen=True, slots=True, kw_only=True)
 class McpViewerConnectionToolFields:
     """Raw MCP viewer connection arguments before policy resolution."""
 
     port: int
-    host: str
-    transport_mode: TransportMode | None
-    timeout_ms: int | None
+    host: str = "localhost"
+    transport_mode: TransportMode | None = None
+    timeout_ms: int | None = None
+
+    @classmethod
+    def signature_parameters(
+        cls,
+        timeout_policy: type[McpControlTimeoutPolicy],
+    ) -> tuple[Parameter, ...]:
+        """Project the public tool signature from the declared field types."""
+        annotations = get_type_hints(cls)
+        return tuple(
+            parameter.replace(
+                annotation=(
+                    _timeout_parameter_annotation(timeout_policy)
+                    if parameter.name == "timeout_ms"
+                    else annotations[parameter.name]
+                )
+            )
+            for parameter in inspect_signature(cls).parameters.values()
+        )
 
     def to_control_args(
         self,
diff --git a/tests/integration/test_cellprofiler_official30_zmq.py b/tests/integration/test_cellprofiler_official30_zmq.py
index a6657b84b..4489bbb40 100644
--- a/tests/integration/test_cellprofiler_official30_zmq.py
+++ b/tests/integration/test_cellprofiler_official30_zmq.py
@@ -193,12 +193,12 @@ def _free_zmq_port_pair(excluded: set[int]) -> int:
 
 def _registered_streaming_config_kwargs(
     viewer_specs: Sequence[StreamingViewerConfigSpec],
-    ports_by_viewer: Mapping[str, int],
+    ports_by_viewer: Mapping[ViewerType, int],
 ) -> dict[str, StreamingConfig]:
     """Project one viewer selection through registered config owners."""
 
     selected_specs = {spec.registry_key: spec for spec in viewer_specs}
-    selected_viewers = {spec.viewer_type.value for spec in viewer_specs}
+    selected_viewers = {spec.viewer_type for spec in viewer_specs}
     if len(selected_specs) != len(viewer_specs) or len(selected_viewers) != len(
         viewer_specs
     ):
@@ -221,7 +221,7 @@ def _registered_streaming_config_kwargs(
         if enabled:
             init_kwargs.update(
                 host="127.0.0.1",
-                port=ports_by_viewer[spec.viewer_type.value],
+                port=ports_by_viewer[spec.viewer_type],
                 transport_mode=TransportMode.TCP,
             )
         config_kwargs[spec.registry_key] = config_type(**init_kwargs)
@@ -523,7 +523,7 @@ def test_official30_fiji_variants_project_registered_viewer_configs() -> None:
 
     for viewer_specs in _OFFICIAL30_FIJI_VIEWER_VARIANTS:
         ports_by_viewer = {
-            spec.viewer_type.value: 20_000 + index * 100
+            spec.viewer_type: 20_000 + index * 100
             for index, spec in enumerate(viewer_specs)
         }
         configs = _registered_streaming_config_kwargs(
@@ -544,7 +544,7 @@ def test_official30_fiji_variants_project_registered_viewer_configs() -> None:
         )
         assert {
             config.viewer_type for config in configs.values() if config.enabled
-        } == {spec.viewer_type.value for spec in viewer_specs}
+        } == {spec.viewer_type for spec in viewer_specs}
         assert all(config.persistent is config.enabled for config in configs.values())
         assert {
             config.viewer_type: config.port
@@ -703,7 +703,7 @@ def test_official30_persistent_fiji_variants_isolated_per_case(
     excluded_ports: set[int] = set()
     execution_port = _free_zmq_port_pair(excluded_ports)
     ports_by_viewer = {
-        spec.viewer_type.value: _free_zmq_port_pair(excluded_ports)
+        spec.viewer_type: _free_zmq_port_pair(excluded_ports)
         for spec in viewer_specs
     }
     streaming_configs = _registered_streaming_config_kwargs(
diff --git a/tests/unit/agent/test_mcp_server.py b/tests/unit/agent/test_mcp_server.py
index 0394ea9d0..e2a984e10 100644
--- a/tests/unit/agent/test_mcp_server.py
+++ b/tests/unit/agent/test_mcp_server.py
@@ -855,11 +855,17 @@ def test_mcp_tool_descriptions_expose_debugging_result_contracts():
     assert "visible_route_keys" in isolate_properties
     assert "selected_route_key" in isolate_properties
     assert "axis_indices" in isolate_properties
-    viewer_validation_properties = schemas["openhcs_validate_viewer_window_state"][
-        "properties"
-    ]
+    viewer_validation_schema = schemas["openhcs_validate_viewer_window_state"]
+    viewer_validation_properties = viewer_validation_schema["properties"]
     assert "route_key" in viewer_validation_properties
     assert "include_state" in viewer_validation_properties
+    assert viewer_validation_properties["transport_mode"]["anyOf"][0] == {
+        "$ref": "#/$defs/TransportMode"
+    }
+    assert viewer_validation_schema["$defs"]["TransportMode"]["enum"] == [
+        "tcp",
+        "ipc",
+    ]
     assert "compact_actions" in schemas["openhcs_ui_get_widget_tree"]["properties"]
     assert (
         "maximum_item_model_nodes"
@@ -14817,6 +14823,22 @@ def test_mcp_viewer_connection_fields_project_timeout_policy():
     )
 
 
+def test_mcp_viewer_connection_tool_fields_parse_nominal_transport_from_wire():
+    control_args = server.McpViewerRequestToolBindingABC.control_args(
+        {
+            "port": 5555,
+            "host": "127.0.0.1",
+            "transport_mode": "tcp",
+            "timeout_ms": 2000,
+        },
+        server.McpViewerCommandTimeoutPolicy,
+    )
+
+    assert control_args.connection.transport_mode is TransportMode.TCP
+    assert control_args.connection.host == "127.0.0.1"
+    assert control_args.timeout_ms == 2000
+
+
 def test_mcp_viewer_mutation_tools_default_to_command_timeout():
     if importlib.util.find_spec("mcp") is None:
         return