diff --git a/jupyter_ai_jupyternaut/models/parameter_schemas.py b/jupyter_ai_jupyternaut/models/parameter_schemas.py
index 6efd7b0..89c64c0 100644
--- a/jupyter_ai_jupyternaut/models/parameter_schemas.py
+++ b/jupyter_ai_jupyternaut/models/parameter_schemas.py
@@ -107,7 +107,7 @@
     },
     "api_base": {
         "type": "string",
-        "description": "Base URL where LLM requests are sent, used for enterprise proxy gateways."
+        "description": "Base URL where LLM requests are sent, used for local models, enterprise proxies, or other hosting providers (e.g. vLLM)."
     }
 }
 
diff --git a/jupyter_ai_jupyternaut/models/parameters_rest_api.py b/jupyter_ai_jupyternaut/models/parameters_rest_api.py
index b7d4971..921d8d5 100644
--- a/jupyter_ai_jupyternaut/models/parameters_rest_api.py
+++ b/jupyter_ai_jupyternaut/models/parameters_rest_api.py
@@ -32,6 +32,9 @@ def get(self):
             
             # Temporary common parameters that work across most models
             common_params = ["temperature", "max_tokens", "top_p", "stop"]
+            # parameters that are actually inputs to the client, not the model
+            # always include these (get_supported_openai_params doesn't include them)
+            client_params = ["api_base"]
             # Params controlling tool availability & usage require a unique UX
             # if they are to be made configurable from the frontend. Therefore
             # they are disabled for now.
@@ -49,7 +52,8 @@ def get(self):
                     parameter_names = common_params
             else:
                 parameter_names = common_params
-            
+            # always include client parameters
+            parameter_names.extend(client_params)
             # Filter out excluded params
             parameter_names = [n for n in parameter_names if n not in EXCLUDED_PARAMS]
             
@@ -109,7 +113,7 @@ def put(self):
                 except ValueError as e:
                     raise HTTPError(400, f"Invalid value for parameter '{param_name}': {str(e)}")
             
-            config_manager = self.settings.get("jai_config_manager")
+            config_manager = self.settings.get("jupyternaut.config_manager")
             if not config_manager:
                 raise HTTPError(500, "Config manager not available")
             
diff --git a/jupyter_ai_jupyternaut/tests/test_handlers.py b/jupyter_ai_jupyternaut/tests/test_handlers.py
index 9f22fa5..d999742 100644
--- a/jupyter_ai_jupyternaut/tests/test_handlers.py
+++ b/jupyter_ai_jupyternaut/tests/test_handlers.py
@@ -1,4 +1,7 @@
 import json
+import pytest
+
+from jupyter_ai_jupyternaut.models import parameter_schemas
 
 
 async def test_get_example(jp_fetch):
@@ -8,6 +11,56 @@ async def test_get_example(jp_fetch):
     # Then
     assert response.code == 200
     payload = json.loads(response.body)
-    assert payload == {
-        "data": "This is /api/jupyternaut/get-example endpoint!"
-    }
\ No newline at end of file
+    assert payload == {"data": "This is /api/jupyternaut/get-example endpoint!"}
+
+
+@pytest.mark.parametrize(
+    "model",
+    [
+        None,
+        "openai/gpt-oss-120b",
+        "hosted_vllm/doesntmatter",
+        "anthropic/claude-3-5-haiku-latest",
+    ],
+)
+async def test_get_parameters(jp_fetch, model):
+    params = {}
+    if model:
+        params["model"] = model
+    response = await jp_fetch("api/jupyternaut/model-parameters", params=params)
+    assert response.code == 200
+    payload = json.loads(response.body)
+    expected_params = [
+        "api_base",
+        "max_tokens",
+        "stop",
+        "temperature",
+        "top_p",
+    ]
+    if model:
+        expected_params.extend(["max_completion_tokens"])
+        if not model.startswith("anthropic/"):
+            expected_params.extend(["frequency_penalty"])
+
+    for param in expected_params:
+        assert param in payload["parameter_names"]
+        assert param in payload["parameters"]
+        assert "description" in payload["parameters"][param]
+
+
+async def test_put_params(jp_fetch):
+    # TODO: validate all types, error handling
+    response = await jp_fetch(
+        "api/jupyternaut/model-parameters",
+        body=json.dumps({
+            "model_id": "hosted_vllm/mlx-community/gpt-oss-20b-MXFP4-Q8",
+            "parameters": {
+                "api_base": {
+                    "value": "http://127.0.0.1:8080",
+                    "type": "string",
+                },
+            },
+        }),
+        method="PUT",
+    )
+    assert response.code == 200