diff --git a/authentication/api/main.py b/authentication/api/main.py
index de510b9..8155329 100644
--- a/authentication/api/main.py
+++ b/authentication/api/main.py
@@ -5,7 +5,7 @@
 import requests
 
 
-from fastapi import FastAPI, Request, Header, HTTPException, Depends, status
+from fastapi import FastAPI, Request, Header, HTTPException, Depends, status, Form
 from fastapi.security import HTTPBasic, OAuth2PasswordRequestForm
 
 import datetime
@@ -35,21 +35,39 @@ async def test(request: Request) -> dict:
 
 
 # TODO: mock responses from FAPI api using the responses library
+# response_type: str
+# client_id: int
+# redirect_uri: str
+# code_challenge: str
+# code_challenge_method: str
 
 
 @app.post("/api/v1/par", response_model=models.PushedAuthorizationResponse)
 async def pushed_authorization_request(
-    par: models.ClientPushedAuthorizationRequest,
+    response_type: Annotated[str, Form()],
+    client_id: Annotated[str, Form()],
+    redirect_uri: Annotated[str, Form()],
+    code_challenge: Annotated[str, Form()],
+    code_challenge_method: Annotated[str, Form()],
     x_amzn_mtls_clientcert: Annotated[str | None, Header()] = None,
 ) -> dict:
     """
     Pass the request along to the FAPI api, await the response,
     send it back to the client app
     """
-
+    # Get all arguments and convert to a urlencoded string
+    encoded_parameters = urllib.parse.urlencode(
+        {
+            "response_type": response_type,
+            "client_id": client_id,
+            "redirect_uri": redirect_uri,
+            "code_challenge": code_challenge,
+            "code_challenge_method": code_challenge_method,
+        }
+    )
     payload = {
-        "parameters": urllib.parse.urlencode(par.model_dump()),
-        "client_id": par.client_id,
+        "parameters": encoded_parameters,
+        "client_id": client_id,
         "client_certificate": x_amzn_mtls_clientcert,
     }
     session = requests.Session()
diff --git a/authentication/tests/test_api.py b/authentication/tests/test_api.py
index b3cd90a..417de86 100644
--- a/authentication/tests/test_api.py
+++ b/authentication/tests/test_api.py
@@ -30,7 +30,7 @@ def test_pushed_authorization_request():
     )
     response = client.post(
         "/api/v1/par",
-        json={
+        data={
             "client_id": 123456,
             "redirect_uri": "https://mobile.example.com/cb",
             "code_challenge": "W78hCS0q72DfIHa...kgZkEJuAFaT4",
diff --git a/client.py b/client.py
index b0b7114..04cf854 100644
--- a/client.py
+++ b/client.py
@@ -11,6 +11,7 @@
 
 AUTHENTICATION_API = os.environ.get("AUTHENTICATION_API", "https://0.0.0.0:8000")
 RESOURCE_API = os.environ.get("RESOURCE_API", "https://0.0.0.0:8010")
+
 ROOT_PATH = os.path.dirname(os.path.abspath(__file__))
 CLIENT_CERTIFICATE = f"{ROOT_PATH}/certs/client-cert.pem"
 CLIENT_PRIVATE_KEY = f"{ROOT_PATH}/certs/client-key.pem"
@@ -27,7 +28,7 @@ def pushed_authorization_request():
 
     response = requests.post(
         f"{AUTHENTICATION_API}/api/v1/par",
-        json={
+        data={
             "response_type": "code",
             "client_id": f"{conf.CLIENT_ID}",
             "redirect_uri": "https://mobile.example.com/cb",