diff --git a/src/mock_vws/_constants.py b/src/mock_vws/_constants.py
index 68bf9375f..52c88bb9b 100644
--- a/src/mock_vws/_constants.py
+++ b/src/mock_vws/_constants.py
@@ -62,6 +62,7 @@ class ResultCodes(Enum):
     TOO_MANY_REQUESTS = "TooManyRequests"
     INVALID_ACCEPT_HEADER = "InvalidAcceptHeader"
     INVALID_INSTANCE_ID = "InvalidInstanceId"
+    BAD_REQUEST = "BadRequest"
 
 
 @beartype
diff --git a/src/mock_vws/_services_validators/__init__.py b/src/mock_vws/_services_validators/__init__.py
index 44487b365..03a39bd1c 100644
--- a/src/mock_vws/_services_validators/__init__.py
+++ b/src/mock_vws/_services_validators/__init__.py
@@ -103,7 +103,7 @@ def run_services_validators(
     validate_date_format(request_headers=request_headers)
     validate_date_in_range(request_headers=request_headers)
 
-    validate_json(request_body=request_body)
+    validate_json(request_body=request_body, request_path=request_path)
 
     validate_keys(
         request_body=request_body,
diff --git a/src/mock_vws/_services_validators/exceptions.py b/src/mock_vws/_services_validators/exceptions.py
index f7cbe2439..a722f29ab 100644
--- a/src/mock_vws/_services_validators/exceptions.py
+++ b/src/mock_vws/_services_validators/exceptions.py
@@ -184,6 +184,46 @@ def __init__(self, *, status_code: HTTPStatus) -> None:
         }
 
 
+@beartype
+class BadRequestError(ValidatorError):
+    """Exception raised when Vuforia returns a response with a result code
+    'BadRequest'.
+    """
+
+    def __init__(self) -> None:
+        """
+        Attributes:
+            status_code: The status code to use in a response if this is
+                raised.
+            response_text: The response text to use in a response if this
+        is
+                raised.
+        """
+        super().__init__()
+        self.status_code = HTTPStatus.BAD_REQUEST
+        body = {
+            "transaction_id": uuid.uuid4().hex,
+            "result_code": ResultCodes.BAD_REQUEST.value,
+        }
+        self.response_text = json_dump(body=body)
+        date = email.utils.formatdate(
+            timeval=None,
+            localtime=False,
+            usegmt=True,
+        )
+        self.headers = {
+            "Connection": "keep-alive",
+            "Content-Type": "application/json",
+            "server": "envoy",
+            "Date": date,
+            "x-envoy-upstream-service-time": "5",
+            "Content-Length": str(object=len(self.response_text)),
+            "strict-transport-security": "max-age=31536000",
+            "x-aws-region": "us-east-2, us-west-2",
+            "x-content-type-options": "nosniff",
+        }
+
+
 @beartype
 class MetadataTooLargeError(ValidatorError):
     """Exception raised when Vuforia returns a response with a result code
diff --git a/src/mock_vws/_services_validators/json_validators.py b/src/mock_vws/_services_validators/json_validators.py
index 9d04eec29..4e0549cd0 100644
--- a/src/mock_vws/_services_validators/json_validators.py
+++ b/src/mock_vws/_services_validators/json_validators.py
@@ -8,6 +8,7 @@
 from beartype import beartype
 
 from mock_vws._services_validators.exceptions import (
+    BadRequestError,
     FailError,
     UnnecessaryRequestBodyError,
 )
@@ -43,14 +44,18 @@ def validate_body_given(*, request_body: bytes, request_method: str) -> None:
 
 
 @beartype
-def validate_json(*, request_body: bytes) -> None:
+def validate_json(*, request_body: bytes, request_path: str) -> None:
     """Validate that any given body is valid JSON.
 
     Args:
         request_body: The body of the request.
+        request_path: The path of the request.
 
     Raises:
-        FailError: The request body includes invalid JSON.
+        BadRequestError: The request body includes invalid JSON for the
+            VuMark instance generation endpoint.
+        FailError: The request body includes invalid JSON for other
+            endpoints.
     """
     if not request_body:
         return
@@ -59,4 +64,6 @@ def validate_json(*, request_body: bytes) -> None:
         json.loads(s=request_body.decode())
     except JSONDecodeError as exc:
         _LOGGER.warning(msg="The request body is not valid JSON.")
+        if request_path.endswith("/instances"):
+            raise BadRequestError from exc
         raise FailError(status_code=HTTPStatus.BAD_REQUEST) from exc
diff --git a/tests/conftest.py b/tests/conftest.py
index 64ef1427f..76b970470 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -85,6 +85,7 @@ def target_id(
         "target_summary",
         "update_target",
         "query",
+        "vumark_generate_instance",
     ],
 )
 def endpoint(request: pytest.FixtureRequest) -> Endpoint:
diff --git a/tests/mock_vws/fixtures/prepared_requests.py b/tests/mock_vws/fixtures/prepared_requests.py
index 6a1d93aa8..724ea8e27 100644
--- a/tests/mock_vws/fixtures/prepared_requests.py
+++ b/tests/mock_vws/fixtures/prepared_requests.py
@@ -5,6 +5,7 @@
 import json
 from http import HTTPMethod, HTTPStatus
 from typing import Any
+from uuid import uuid4
 
 import pytest
 from urllib3.filepost import encode_multipart_formdata
@@ -13,6 +14,7 @@
 
 from mock_vws._constants import ResultCodes
 from mock_vws.database import VuforiaDatabase
+from tests.mock_vws.fixtures.credentials import VuMarkVuforiaDatabase
 from tests.mock_vws.utils import Endpoint
 from tests.mock_vws.utils.retries import RETRY_ON_TOO_MANY_REQUESTS
 
@@ -451,3 +453,49 @@ def query(
         access_key=access_key,
         secret_key=secret_key,
     )
+
+
+@pytest.fixture
+def vumark_generate_instance(
+    vumark_vuforia_database: VuMarkVuforiaDatabase,
+) -> Endpoint:
+    """Return details of the endpoint for generating a VuMark instance."""
+    request_path = f"/targets/{vumark_vuforia_database.target_id}/instances"
+    content_type = "application/json"
+    method = HTTPMethod.POST
+    content = json.dumps(obj={"instance_id": uuid4().hex}).encode(
+        encoding="utf-8"
+    )
+    date = rfc_1123_date()
+
+    access_key = vumark_vuforia_database.server_access_key
+    secret_key = vumark_vuforia_database.server_secret_key
+    authorization_string = authorization_header(
+        access_key=access_key,
+        secret_key=secret_key,
+        method=method,
+        content=content,
+        content_type=content_type,
+        date=date,
+        request_path=request_path,
+    )
+
+    headers = {
+        "Accept": "image/png",
+        "Authorization": authorization_string,
+        "Content-Length": str(object=len(content)),
+        "Content-Type": content_type,
+        "Date": date,
+    }
+
+    return Endpoint(
+        successful_headers_status_code=HTTPStatus.OK,
+        successful_headers_result_code=None,
+        base_url=VWS_HOST,
+        path_url=request_path,
+        method=method,
+        headers=headers,
+        data=content,
+        access_key=access_key,
+        secret_key=secret_key,
+    )
diff --git a/tests/mock_vws/test_date_header.py b/tests/mock_vws/test_date_header.py
index eea178ac3..d5e5f0b45 100644
--- a/tests/mock_vws/test_date_header.py
+++ b/tests/mock_vws/test_date_header.py
@@ -381,6 +381,12 @@ def test_date_in_range_after(endpoint: Endpoint) -> None:
             assert_query_success(response=response)
             return
 
+        if endpoint.successful_headers_result_code is None:
+            assert (
+                response.status_code == endpoint.successful_headers_status_code
+            )
+            return
+
         assert_vws_response(
             response=response,
             status_code=endpoint.successful_headers_status_code,
@@ -445,6 +451,12 @@ def test_date_in_range_before(endpoint: Endpoint) -> None:
             assert_query_success(response=response)
             return
 
+        if endpoint.successful_headers_result_code is None:
+            assert (
+                response.status_code == endpoint.successful_headers_status_code
+            )
+            return
+
         assert_vws_response(
             response=response,
             status_code=endpoint.successful_headers_status_code,
diff --git a/tests/mock_vws/test_invalid_json.py b/tests/mock_vws/test_invalid_json.py
index 55d01ff6d..35b3253cd 100644
--- a/tests/mock_vws/test_invalid_json.py
+++ b/tests/mock_vws/test_invalid_json.py
@@ -75,10 +75,15 @@ def test_invalid_json(endpoint: Endpoint) -> None:
         assert_valid_date_header(response=response)
 
         if takes_json_data:
+            expected_result_code = (
+                ResultCodes.BAD_REQUEST
+                if endpoint.path_url.endswith("/instances")
+                else ResultCodes.FAIL
+            )
             assert_vws_failure(
                 response=response,
                 status_code=HTTPStatus.BAD_REQUEST,
-                result_code=ResultCodes.FAIL,
+                result_code=expected_result_code,
             )
             return
 
diff --git a/tests/mock_vws/utils/__init__.py b/tests/mock_vws/utils/__init__.py
index c554e4571..d4bfa0014 100644
--- a/tests/mock_vws/utils/__init__.py
+++ b/tests/mock_vws/utils/__init__.py
@@ -47,7 +47,7 @@ class Endpoint:
     method: str
     headers: Mapping[str, str]
     data: bytes | str
-    successful_headers_result_code: ResultCodes
+    successful_headers_result_code: ResultCodes | None
     successful_headers_status_code: int
     access_key: str
     secret_key: str