fix(server): preserve legacy elicitation errors

Signed-off-by: Ruiming Zhao <uuzzrm@gmail.com>

Author: uuzzrm

src/mcp/server/elicitation.py

@@ -13,6 +13,7 @@
 from pydantic_core import core_schema
 from typing_extensions import TypeAliasType
 
+from mcp.server.mcpserver.exceptions import ToolError
 from mcp.server.session import ServerSession
 
 ElicitSchemaModelT = TypeVar("ElicitSchemaModelT", bound=BaseModel)
@@ -116,7 +117,7 @@ async def elicit_with_validation(
     For sensitive data like credentials or OAuth flows, use elicit_url() instead.
 
     Raises:
-        ValueError: If the client accepted the elicitation without supplying
+        ToolError: If the client accepted the elicitation without supplying
             content, or with content that does not match the requested schema.
     """
     json_schema = render_elicitation_schema(schema)
@@ -129,13 +130,11 @@ async def elicit_with_validation(
 
     if result.action == "accept":
         if result.content is None:
-            raise ValueError("Received an accepted elicitation with no content")
+            raise ToolError("Received an accepted elicitation with no content")
         try:
             validated_data = schema.model_validate(result.content)
         except ValidationError as e:
-            raise ValueError(
-                "Received an accepted elicitation whose content does not match the requested schema"
-            ) from e
+            raise ToolError("Received an accepted elicitation whose content does not match the requested schema") from e
         return AcceptedElicitation(data=validated_data)
     if result.action == "decline":
         return DeclinedElicitation()

tests/interaction/mcpserver/test_prompts.py

@@ -124,7 +124,7 @@ async def test_get_prompt_with_a_wrong_type_argument_is_rejected_before_the_func
     The decorated function is wrapped in pydantic's validate_call, so a value that cannot be
     coerced to the parameter's annotation fails before the body executes. The function body
     raises NotImplementedError to prove it never ran. The error is logged server-side and the
-    client receives the same sanitized tool result as other unexpected exceptions.
+    client receives the raw validation message with the stable rendering-error prefix.
     """
     mcp = MCPServer("prompter")
 

tests/server/mcpserver/test_resolve.py

@@ -1051,7 +1051,7 @@ async def empty_accept(context: ClientRequestContext, params: ElicitRequestParam
         if mode == "auto":
             assert "received an accepted elicitation with no content" in result.content[0].text
         else:
-            assert result.content[0].text == "An unexpected error occurred while executing tool tool"
+            assert result.content[0].text == "Received an accepted elicitation with no content"
 
 
 @pytest.mark.anyio
@@ -1432,7 +1432,7 @@ async def whoami(login: Annotated[Login, Resolve(ask)]) -> str:
             assert "does not match the requested schema" in text
             assert "Resolver" in text
         else:
-            assert text == "An unexpected error occurred while executing tool whoami"
+            assert text == "Received an accepted elicitation whose content does not match the requested schema"
         assert "errors.pydantic.dev" not in text