diff --git a/pyrit/backend/models/attacks.py b/pyrit/backend/models/attacks.py
index 3b280c09d6..3f8e12b386 100644
--- a/pyrit/backend/models/attacks.py
+++ b/pyrit/backend/models/attacks.py
@@ -16,6 +16,7 @@
 
 from pyrit.backend.models._media import build_filename, infer_mime_type
 from pyrit.backend.models.common import (
+    MAX_IDENTIFIER_LENGTH,
     MAX_ITEMS,
     IdentifierStr,
     LabelDict,
@@ -600,7 +601,7 @@ class SaveConversationRequest(_AttackAttributionInput):
     source_conversation_id: uuid.UUID | None = None
     expected_objective: str | None = None
     objective: str | None = Field(None, description="Omit to keep the destination's objective unchanged")
-    target_registry_name: str | None = None
+    target_registry_name: IdentifierStr | None = None
     messages: list[MessageRequest] = Field(default_factory=list)
 
     @model_validator(mode="after")
@@ -701,10 +702,16 @@ class AddMessageRequest(MessageRequest):
         description="Ordered registry-backed converter pipelines to apply to the response.",
     )
     start_token: str = Field(
-        default="⟪", min_length=1, description="Opening marker for request and response converter pipelines"
+        default="⟪",
+        min_length=1,
+        max_length=MAX_IDENTIFIER_LENGTH,
+        description="Opening marker for request and response converter pipelines",
     )
     end_token: str = Field(
-        default="⟫", min_length=1, description="Closing marker for request and response converter pipelines"
+        default="⟫",
+        min_length=1,
+        max_length=MAX_IDENTIFIER_LENGTH,
+        description="Closing marker for request and response converter pipelines",
     )
     target_conversation_id: IdentifierStr = Field(
         ...,
diff --git a/pyrit/backend/models/converters.py b/pyrit/backend/models/converters.py
index 28c5a46f40..476d48d31b 100644
--- a/pyrit/backend/models/converters.py
+++ b/pyrit/backend/models/converters.py
@@ -11,7 +11,12 @@
 
 from pydantic import BaseModel, Field
 
-from pyrit.backend.models.common import MAX_ITEMS, REGISTRY_INSTANCE_NAME_PATTERN, IdentifierStr
+from pyrit.backend.models.common import (
+    MAX_IDENTIFIER_LENGTH,
+    MAX_ITEMS,
+    REGISTRY_INSTANCE_NAME_PATTERN,
+    IdentifierStr,
+)
 from pyrit.models import ConverterIdentifier, Parameter, PromptDataType
 
 __all__ = [
@@ -119,8 +124,18 @@ class ConverterPreviewRequest(BaseModel):
     original_value: str = Field(..., description="Text to convert")
     original_value_data_type: PromptDataType = Field(default="text", description="Data type of original value")
     converter_ids: list[IdentifierStr] = Field(..., max_length=MAX_ITEMS, description="Converter instance IDs to apply")
-    start_token: str = Field(default="⟪", min_length=1, description="Opening marker for selected text regions")
-    end_token: str = Field(default="⟫", min_length=1, description="Closing marker for selected text regions")
+    start_token: str = Field(
+        default="⟪",
+        min_length=1,
+        max_length=MAX_IDENTIFIER_LENGTH,
+        description="Opening marker for selected text regions",
+    )
+    end_token: str = Field(
+        default="⟫",
+        min_length=1,
+        max_length=MAX_IDENTIFIER_LENGTH,
+        description="Closing marker for selected text regions",
+    )
 
 
 class ConverterPreviewResponse(BaseModel):
diff --git a/pyrit/backend/models/scorers.py b/pyrit/backend/models/scorers.py
index 2da03a09d8..966eba2779 100644
--- a/pyrit/backend/models/scorers.py
+++ b/pyrit/backend/models/scorers.py
@@ -5,7 +5,7 @@
 
 from pydantic import BaseModel, Field
 
-from pyrit.backend.models.common import REGISTRY_INSTANCE_NAME_PATTERN, PaginationInfo
+from pyrit.backend.models.common import MAX_ITEMS, REGISTRY_INSTANCE_NAME_PATTERN, IdentifierStr, PaginationInfo
 from pyrit.models import JSONValue, Parameter
 from pyrit.models.catalog.scorer import ScorerInstance
 
@@ -36,5 +36,7 @@ class CreateScorerRequest(BaseModel):
     """Request to construct and register a named scorer."""
 
     name: str = Field(..., min_length=1, pattern=REGISTRY_INSTANCE_NAME_PATTERN, description="Unique registry name")
-    type: str = Field(..., description="Scorer class name")
-    params: dict[str, JSONValue] = Field(default_factory=dict, description="Scorer constructor parameters")
+    type: IdentifierStr = Field(..., description="Scorer class name")
+    params: dict[IdentifierStr, JSONValue] = Field(
+        default_factory=dict, max_length=MAX_ITEMS, description="Scorer constructor parameters"
+    )
diff --git a/pyrit/backend/models/techniques.py b/pyrit/backend/models/techniques.py
index 1e3aebaf63..35e64d85a4 100644
--- a/pyrit/backend/models/techniques.py
+++ b/pyrit/backend/models/techniques.py
@@ -7,7 +7,7 @@
 
 from pydantic import BaseModel, ConfigDict, Field, JsonValue, field_validator
 
-from pyrit.backend.models.common import PaginationInfo
+from pyrit.backend.models.common import IdentifierStr, PaginationInfo, TextStr
 from pyrit.models import Parameter
 from pyrit.models.request_limits import MAX_ITEMS
 
@@ -56,12 +56,12 @@ class CreateTechniqueRequest(BaseModel):
 
     name: TechniqueSelector
     type: str = Field(min_length=1, max_length=256)
-    params: dict[str, JsonValue] = Field(default_factory=dict, max_length=MAX_ITEMS)
-    description: str | None = None
+    params: dict[IdentifierStr, JsonValue] = Field(default_factory=dict, max_length=MAX_ITEMS)
+    description: TextStr | None = None
     tags: list[TechniqueSelector] = Field(default_factory=list, max_length=MAX_ITEMS)
-    request_converters: list[str] | None = Field(default=None, max_length=MAX_ITEMS)
-    response_converters: list[str] | None = Field(default=None, max_length=MAX_ITEMS)
-    adversarial_chat: str | None = None
+    request_converters: list[IdentifierStr] | None = Field(default=None, max_length=MAX_ITEMS)
+    response_converters: list[IdentifierStr] | None = Field(default=None, max_length=MAX_ITEMS)
+    adversarial_chat: IdentifierStr | None = None
     adversarial_system_prompt: str | None = None
     adversarial_seed_prompt: str | None = None
     adversarial_prompt_template: str | None = None
diff --git a/pyrit/backend/routes/attacks.py b/pyrit/backend/routes/attacks.py
index bb75f1f33b..82766a713c 100644
--- a/pyrit/backend/routes/attacks.py
+++ b/pyrit/backend/routes/attacks.py
@@ -33,6 +33,7 @@
     UpdateMainConversationResponse,
 )
 from pyrit.backend.models.common import (
+    MAX_IDENTIFIER_LENGTH,
     MAX_ITEMS,
     CursorStr,
     IdentifierStr,
@@ -352,7 +353,9 @@ async def remove_human_score(attack_result_id: IdentifierStr) -> AttackSummary:
 )
 async def get_conversation_messages(  # pyrit-async-suffix-exempt
     attack_result_id: IdentifierStr,
-    conversation_id: IdentifierStr = Query(..., description="The conversation_id whose messages to return"),
+    conversation_id: str = Query(
+        ..., max_length=MAX_IDENTIFIER_LENGTH, description="The conversation_id whose messages to return"
+    ),
 ) -> ConversationMessagesResponse:
     """
     Get all messages for a conversation belonging to an attack.
diff --git a/pyrit/backend/routes/datasets.py b/pyrit/backend/routes/datasets.py
index 7dc342be94..5b0ea397d6 100644
--- a/pyrit/backend/routes/datasets.py
+++ b/pyrit/backend/routes/datasets.py
@@ -8,11 +8,19 @@
 discovered from registered ``SeedDatasetProvider`` subclasses and from memory.
 """
 
+from typing import Annotated
 from uuid import UUID
 
 from fastapi import APIRouter, HTTPException, Query, status
-
-from pyrit.backend.models.common import MAX_ITEMS, CursorStr, ProblemDetail
+from pydantic import Field
+
+from pyrit.backend.models.common import (
+    MAX_CURSOR_LENGTH,
+    MAX_ITEMS,
+    MAX_LABEL_VALUE_LENGTH,
+    CursorStr,
+    ProblemDetail,
+)
 from pyrit.backend.models.datasets import (
     DatasetListResponse,
     SeedExampleDetailResponse,
@@ -55,7 +63,7 @@ async def list_datasets(loaded_only: bool = False) -> DatasetListResponse:  # py
     },
 )
 async def list_seed_examples(  # pyrit-async-suffix-exempt
-    selection_key: str = Query(..., description=_SELECTION_KEY_DESCRIPTION),
+    selection_key: str = Query(..., max_length=MAX_CURSOR_LENGTH, description=_SELECTION_KEY_DESCRIPTION),
     limit: int = Query(20, ge=1, le=100, description="Maximum examples per page"),
     cursor: CursorStr | None = Query(
         None,
@@ -68,7 +76,7 @@ async def list_seed_examples(  # pyrit-async-suffix-exempt
         description="Case-insensitive literal text to find in text prompt and objective values",
     ),
     modality: list[PromptDataType] | None = Query(None, max_length=MAX_ITEMS, description="Data types, OR-matched"),
-    harm_category: list[str] | None = Query(
+    harm_category: list[Annotated[str, Field(max_length=MAX_LABEL_VALUE_LENGTH)]] | None = Query(
         None, max_length=MAX_ITEMS, description="Whole harm categories, case-insensitive, OR-matched"
     ),
     seed_type: list[SeedType] | None = Query(None, max_length=MAX_ITEMS, description="Seed types, OR-matched"),
@@ -103,7 +111,7 @@ async def list_seed_examples(  # pyrit-async-suffix-exempt
 )
 async def get_seed_example(  # pyrit-async-suffix-exempt
     example_id: UUID,
-    selection_key: str = Query(..., description=_SELECTION_KEY_DESCRIPTION),
+    selection_key: str = Query(..., max_length=MAX_CURSOR_LENGTH, description=_SELECTION_KEY_DESCRIPTION),
 ) -> SeedExampleDetailResponse:
     """
     Get one stored logical seed example with all of its members.
diff --git a/pyrit/backend/routes/message_sends.py b/pyrit/backend/routes/message_sends.py
index 6099305c10..73460e3b13 100644
--- a/pyrit/backend/routes/message_sends.py
+++ b/pyrit/backend/routes/message_sends.py
@@ -8,7 +8,7 @@
 
 from fastapi import APIRouter, HTTPException, Query, status
 
-from pyrit.backend.models.common import ProblemDetail
+from pyrit.backend.models.common import IdentifierStr, ProblemDetail
 from pyrit.backend.models.message_sends import MessageSendRequest, MessageSendStatus
 from pyrit.backend.services.attack_service import get_attack_service
 from pyrit.backend.services.manual_send_scheduler import ManualSendConflictError, ManualSendQueueFullError
@@ -30,7 +30,9 @@
         429: {"model": ProblemDetail, "description": "Manual-message admission unavailable"},
     },
 )
-async def submit_message_send_async(*, attack_result_id: str, request: MessageSendRequest) -> MessageSendStatus:
+async def submit_message_send_async(
+    *, attack_result_id: IdentifierStr, request: MessageSendRequest
+) -> MessageSendStatus:
     """Return a transient handle after validation and admission, before preparation or target I/O."""
     try:
         return await get_attack_service().submit_message_send_async(attack_result_id=attack_result_id, request=request)
@@ -51,7 +53,7 @@ async def submit_message_send_async(*, attack_result_id: str, request: MessageSe
     responses={404: {"model": ProblemDetail, "description": "Handle expired, missing, or for another attack"}},
 )
 async def get_message_send_async(
-    *, attack_result_id: str, send_id: str, wait_ms: Annotated[int, Query(ge=0, le=1000)] = 0
+    *, attack_result_id: IdentifierStr, send_id: IdentifierStr, wait_ms: Annotated[int, Query(ge=0, le=1000)] = 0
 ) -> MessageSendStatus:
     """
     Read progress, optionally waiting briefly without cancelling or resubmitting the accepted work.
diff --git a/pyrit/backend/routes/scorers.py b/pyrit/backend/routes/scorers.py
index 6635f10eff..60e8b15dee 100644
--- a/pyrit/backend/routes/scorers.py
+++ b/pyrit/backend/routes/scorers.py
@@ -5,7 +5,7 @@
 
 from fastapi import APIRouter, HTTPException, Query, status
 
-from pyrit.backend.models.common import ProblemDetail
+from pyrit.backend.models.common import CursorStr, IdentifierStr, ProblemDetail
 from pyrit.backend.models.scorers import (
     CreateScorerRequest,
     ScorerListResponse,
@@ -31,7 +31,7 @@ async def list_scorer_types() -> ScorerTypeResponse:  # pyrit-async-suffix-exemp
 @router.get("", response_model=ScorerListResponse)
 async def list_scorers(
     limit: int = Query(50, ge=1, le=200, description="Maximum items per page"),
-    cursor: str | None = Query(None, description="Scorer registry name to start after"),
+    cursor: CursorStr | None = Query(None, description="Scorer registry name to start after"),
 ) -> ScorerListResponse:  # pyrit-async-suffix-exempt
     """
     List named scorer instances with pagination.
@@ -71,7 +71,7 @@ async def create_scorer(request: CreateScorerRequest) -> ScorerInstance:  # pyri
     response_model=ScorerInstance,
     responses={404: {"model": ProblemDetail, "description": "Scorer not found"}},
 )
-async def get_scorer(scorer_registry_name: str) -> ScorerInstance:  # pyrit-async-suffix-exempt
+async def get_scorer(scorer_registry_name: IdentifierStr) -> ScorerInstance:  # pyrit-async-suffix-exempt
     """
     Get a named scorer instance.
 
diff --git a/tests/unit/backend/test_api_routes.py b/tests/unit/backend/test_api_routes.py
index 2fe2d9286d..077102d445 100644
--- a/tests/unit/backend/test_api_routes.py
+++ b/tests/unit/backend/test_api_routes.py
@@ -870,6 +870,15 @@ def test_get_attack_rejects_oversized_id(self, client: TestClient) -> None:
             assert response.status_code == status.HTTP_422_UNPROCESSABLE_CONTENT
             mock_get_service.assert_not_called()
 
+    def test_get_conversation_messages_rejects_oversized_conversation_id(self, client: TestClient) -> None:
+        with patch("pyrit.backend.routes.attacks.get_attack_service") as mock_get_service:
+            response = client.get(
+                "/api/attacks/attack/messages", params={"conversation_id": "c" * (MAX_IDENTIFIER_LENGTH + 1)}
+            )
+
+            assert response.status_code == status.HTTP_422_UNPROCESSABLE_CONTENT
+            mock_get_service.assert_not_called()
+
     def test_parse_labels_value_with_extra_colons(self, client: TestClient) -> None:
         """Test that _parse_labels handles values containing colons (split on first only)."""
         with patch("pyrit.backend.routes.attacks.get_attack_service") as mock_get_service:
diff --git a/tests/unit/backend/test_common_models.py b/tests/unit/backend/test_common_models.py
index 10c062fec8..0e63b7958a 100644
--- a/tests/unit/backend/test_common_models.py
+++ b/tests/unit/backend/test_common_models.py
@@ -14,6 +14,7 @@
     AddMessageRequest,
     CreateAttackRequest,
     MessagePieceRequest,
+    SaveConversationRequest,
     UpdateAttackRequest,
 )
 from pyrit.backend.models.common import (
@@ -38,6 +39,7 @@
 from pyrit.backend.models.initializers import RegisterInitializerRequest
 from pyrit.backend.models.scores import ManualScoreRequest
 from pyrit.backend.models.targets import CreateTargetRequest
+from pyrit.backend.models.techniques import CreateTechniqueRequest
 
 
 class TestPaginationInfo:
@@ -446,6 +448,8 @@ def test_update_attack_request_expected_objective_is_not_length_limited() -> Non
         {"converter_ids": ["converter"] * (MAX_ITEMS + 1)},
         {"request_converter_configurations": [{"converter_ids": ["converter"]}] * (MAX_ITEMS + 1)},
         {"pieces": [{"original_value": "text", "mime_type": "m" * (MAX_IDENTIFIER_LENGTH + 1)}]},
+        {"start_token": "s" * (MAX_IDENTIFIER_LENGTH + 1)},
+        {"end_token": "e" * (MAX_IDENTIFIER_LENGTH + 1)},
     ],
 )
 def test_add_message_request_rejects_values_over_limits(overrides: dict[str, object]) -> None:
@@ -478,7 +482,51 @@ def test_message_piece_content_is_not_length_limited() -> None:
             "params",
         ),
         (ConverterPreviewRequest, {"original_value": "x", "converter_ids": ["c"] * (MAX_ITEMS + 1)}, "converter_ids"),
+        (
+            ConverterPreviewRequest,
+            {"original_value": "x", "converter_ids": [], "start_token": "s" * (MAX_IDENTIFIER_LENGTH + 1)},
+            "start_token",
+        ),
+        (
+            ConverterPreviewRequest,
+            {"original_value": "x", "converter_ids": [], "end_token": "e" * (MAX_IDENTIFIER_LENGTH + 1)},
+            "end_token",
+        ),
+        (
+            CreateTechniqueRequest,
+            {"name": "t", "type": "PromptSendingAttack", "description": "d" * (MAX_TEXT_LENGTH + 1)},
+            "description",
+        ),
+        (
+            CreateTechniqueRequest,
+            {"name": "t", "type": "RedTeamingAttack", "adversarial_chat": "a" * (MAX_IDENTIFIER_LENGTH + 1)},
+            "adversarial_chat",
+        ),
+        (
+            CreateTechniqueRequest,
+            {"name": "t", "type": "PromptSendingAttack", "request_converters": ["c" * (MAX_IDENTIFIER_LENGTH + 1)]},
+            "request_converters",
+        ),
+        (
+            CreateTechniqueRequest,
+            {"name": "t", "type": "PromptSendingAttack", "response_converters": ["c" * (MAX_IDENTIFIER_LENGTH + 1)]},
+            "response_converters",
+        ),
+        (
+            CreateTechniqueRequest,
+            {"name": "t", "type": "PromptSendingAttack", "params": {"p" * (MAX_IDENTIFIER_LENGTH + 1): 1}},
+            "params",
+        ),
         (CreateTargetRequest, {"type": "t" * (MAX_IDENTIFIER_LENGTH + 1)}, "type"),
+        (
+            SaveConversationRequest,
+            {
+                "save_id": str(uuid.uuid4()),
+                "destination": "new_attack",
+                "target_registry_name": "t" * (MAX_IDENTIFIER_LENGTH + 1),
+            },
+            "target_registry_name",
+        ),
         (
             ManualScoreRequest,
             {
@@ -500,6 +548,20 @@ def test_request_models_reject_values_over_limits(
     assert [item["loc"][0] for item in error.value.errors()] == [field]
 
 
+def test_create_technique_request_accepts_values_at_limits() -> None:
+    request = CreateTechniqueRequest(
+        name="t",
+        type="RedTeamingAttack",
+        description="d" * MAX_TEXT_LENGTH,
+        adversarial_chat="a" * MAX_IDENTIFIER_LENGTH,
+        request_converters=["c" * MAX_IDENTIFIER_LENGTH],
+        params={"p" * MAX_IDENTIFIER_LENGTH: 1},
+        adversarial_system_prompt="s" * (MAX_TEXT_LENGTH + 1),
+    )
+
+    assert len(request.adversarial_system_prompt or "") == MAX_TEXT_LENGTH + 1
+
+
 def test_label_filter_limits_ignore_surrounding_whitespace() -> None:
     padded = f"  {'k' * MAX_LABEL_KEY_LENGTH}  :  {'v' * MAX_LABEL_VALUE_LENGTH}  "
 
diff --git a/tests/unit/backend/test_message_send_routes.py b/tests/unit/backend/test_message_send_routes.py
index 43d2b0e3e7..e77127da77 100644
--- a/tests/unit/backend/test_message_send_routes.py
+++ b/tests/unit/backend/test_message_send_routes.py
@@ -10,6 +10,7 @@
 from fastapi.testclient import TestClient
 
 from pyrit.backend.main import app
+from pyrit.backend.models.common import MAX_IDENTIFIER_LENGTH
 from pyrit.backend.models.message_sends import MessageSendStatus
 from pyrit.backend.services.attack_service import AttackService
 from pyrit.backend.services.manual_send_scheduler import ManualSendConflictError, ManualSendQueueFullError
@@ -146,3 +147,14 @@ def test_missing_handle_is_not_recreated(*, client: TestClient, sender: MagicMoc
     assert response.status_code == 404
     assert "do not resend" in response.json()["detail"]
     sender.submit_async.assert_not_awaited()
+
+
+def test_oversized_identifiers_are_rejected_before_the_services(
+    *, client: TestClient, sender: MagicMock, payload: dict[str, object]
+) -> None:
+    oversized = "a" * (MAX_IDENTIFIER_LENGTH + 1)
+
+    assert client.post(f"/api/attacks/{oversized}/message-sends", json=payload).status_code == 422
+    assert client.get(f"/api/attacks/attack/message-sends/{oversized}").status_code == 422
+    sender.submit_async.assert_not_awaited()
+    sender.get_status_async.assert_not_awaited()
diff --git a/tests/unit/backend/test_scorer_routes.py b/tests/unit/backend/test_scorer_routes.py
index 25339d3267..b58176f721 100644
--- a/tests/unit/backend/test_scorer_routes.py
+++ b/tests/unit/backend/test_scorer_routes.py
@@ -10,6 +10,7 @@
 from fastapi.testclient import TestClient
 
 from pyrit.backend.main import app
+from pyrit.backend.models.common import MAX_CURSOR_LENGTH, MAX_IDENTIFIER_LENGTH, MAX_ITEMS
 from pyrit.backend.services.scorer_service import get_scorer_service
 from pyrit.models import ComponentIdentifier, Scorable, Score, ScoringExpectation, TargetIdentifier
 from pyrit.prompt_target import PromptTarget
@@ -199,6 +200,17 @@ def test_duplicate_name_returns_400_and_does_not_replace_instance(compatibility_
         ("/api/scorers", {"name": "invalid name", "type": "_RouteLeafScorer", "params": {}}),
         ("/api/scorers?limit=0", None),
         ("/api/scorers?limit=201", None),
+        ("/api/scorers", {"name": "valid", "type": "t" * (MAX_IDENTIFIER_LENGTH + 1), "params": {}}),
+        (
+            "/api/scorers",
+            {"name": "valid", "type": "_RouteLeafScorer", "params": {"p" * (MAX_IDENTIFIER_LENGTH + 1): 1}},
+        ),
+        (
+            "/api/scorers",
+            {"name": "valid", "type": "_RouteLeafScorer", "params": {f"p{i}": i for i in range(MAX_ITEMS + 1)}},
+        ),
+        (f"/api/scorers?cursor={'c' * (MAX_CURSOR_LENGTH + 1)}", None),
+        (f"/api/scorers/{'s' * (MAX_IDENTIFIER_LENGTH + 1)}", None),
     ],
 )
 def test_invalid_scorer_request_shapes_return_422(
diff --git a/tests/unit/backend/test_seed_example_routes.py b/tests/unit/backend/test_seed_example_routes.py
index 0f39b7a9e8..683a7873be 100644
--- a/tests/unit/backend/test_seed_example_routes.py
+++ b/tests/unit/backend/test_seed_example_routes.py
@@ -11,6 +11,7 @@
 from httpx import ASGITransport, AsyncClient
 
 from pyrit.backend.main import app
+from pyrit.backend.models.common import MAX_CURSOR_LENGTH, MAX_LABEL_VALUE_LENGTH
 from pyrit.backend.services.dataset_service import get_dataset_service
 from pyrit.common.utils import to_sha256
 from pyrit.memory import MemoryInterface
@@ -84,6 +85,9 @@ async def test_list_seed_examples_pages_with_a_filter_bound_cursor(client: Async
         ("", {"selection_key": DATASET}, 400),
         ("", {"selection_key": "dataset:named:"}, 400),
         ("", {"selection_key": NAMED, "limit": 0}, 422),
+        ("", {"selection_key": "k" * (MAX_CURSOR_LENGTH + 1)}, 422),
+        ("", {"selection_key": NAMED, "harm_category": "h" * (MAX_LABEL_VALUE_LENGTH + 1)}, 422),
+        (f"/{MISSING_ID}", {"selection_key": "k" * (MAX_CURSOR_LENGTH + 1)}, 422),
         (f"/{MISSING_ID}", {"selection_key": "dataset:other"}, 400),
         (f"/{MISSING_ID}", {"selection_key": NAMED}, 404),
         ("/not-a-uuid", {"selection_key": NAMED}, 422),