fastmcp/tests/client/test_elicitation.py
Jeremiah Lowin acf4db0bf5
Add SEP-1034 default values support for elicitation (#2545)
- Add comprehensive tests for default values in elicitation schemas
- Document default values support in elicitation docs
- Confirms FastMCP automatically supports defaults via Pydantic

Closes #2544
2025-12-04 10:43:48 -05:00

862 lines
30 KiB
Python

from dataclasses import asdict, dataclass
from enum import Enum
from typing import Literal
import pytest
from mcp.types import ElicitRequestParams
from pydantic import BaseModel, Field
from typing_extensions import TypedDict
from fastmcp import Context, FastMCP
from fastmcp.client.client import Client
from fastmcp.client.elicitation import ElicitResult
from fastmcp.exceptions import ToolError
from fastmcp.server.elicitation import (
AcceptedElicitation,
CancelledElicitation,
DeclinedElicitation,
get_elicitation_schema,
validate_elicitation_json_schema,
)
from fastmcp.utilities.types import TypeAdapter
@pytest.fixture
def fastmcp_server():
mcp = FastMCP("TestServer")
@dataclass
class Person:
name: str
@mcp.tool
async def ask_for_name(context: Context) -> str:
result = await context.elicit(
message="What is your name?",
response_type=Person,
)
if result.action == "accept":
return f"Hello, {result.data.name}!" # type: ignore[attr-defined]
else:
return "No name provided."
@mcp.tool
def simple_test() -> str:
return "Hello!"
return mcp
async def test_elicitation_with_no_handler(fastmcp_server):
"""Test that elicitation works without a handler."""
async with Client(fastmcp_server) as client:
with pytest.raises(ToolError, match="Elicitation not supported"):
await client.call_tool("ask_for_name")
async def test_elicitation_accept_content(fastmcp_server):
"""Test basic elicitation functionality."""
async def elicitation_handler(message, response_type, params, ctx):
# Mock user providing their name
return ElicitResult(action="accept", content=response_type(name="Alice"))
async with Client(
fastmcp_server, elicitation_handler=elicitation_handler
) as client:
result = await client.call_tool("ask_for_name")
assert result.data == "Hello, Alice!"
async def test_elicitation_decline(fastmcp_server):
"""Test that elicitation handler receives correct parameters."""
async def elicitation_handler(message, response_type, params, ctx):
return ElicitResult(action="decline")
async with Client(
fastmcp_server, elicitation_handler=elicitation_handler
) as client:
result = await client.call_tool("ask_for_name")
assert result.data == "No name provided."
async def test_elicitation_handler_parameters():
"""Test that elicitation handler receives correct parameters."""
mcp = FastMCP("TestServer")
captured_params = {}
@mcp.tool
async def test_tool(context: Context) -> str:
await context.elicit(
message="Test message",
response_type=int,
)
return "done"
async def elicitation_handler(message, response_type, params, ctx):
captured_params["message"] = message
captured_params["response_type"] = str(response_type)
captured_params["params"] = params
captured_params["ctx"] = ctx
return ElicitResult(action="accept", content={"value": 42})
async with Client(mcp, elicitation_handler=elicitation_handler) as client:
await client.call_tool("test_tool", {})
assert captured_params["message"] == "Test message"
assert "ScalarElicitationType" in str(captured_params["response_type"])
assert captured_params["params"].requestedSchema == {
"properties": {"value": {"title": "Value", "type": "integer"}},
"required": ["value"],
"title": "ScalarElicitationType",
"type": "object",
}
assert captured_params["ctx"] is not None
async def test_elicitation_cancel_action():
"""Test user canceling elicitation request."""
mcp = FastMCP("TestServer")
@mcp.tool
async def ask_for_optional_info(context: Context) -> str:
result = await context.elicit(
message="Optional: What's your age?", response_type=int
)
if result.action == "cancel":
return "Request was canceled"
elif result.action == "accept":
return f"Age: {result.data}" # type: ignore[attr-defined]
else:
return "No response provided"
async def elicitation_handler(message, response_type, params, ctx):
return ElicitResult(action="cancel")
async with Client(mcp, elicitation_handler=elicitation_handler) as client:
result = await client.call_tool("ask_for_optional_info", {})
assert result.data == "Request was canceled"
class TestScalarResponseTypes:
async def test_elicitation_no_response(self):
"""Test elicitation with no response type."""
mcp = FastMCP("TestServer")
@mcp.tool
async def my_tool(context: Context) -> None:
result = await context.elicit(message="", response_type=None)
return result.data # type: ignore[attr-defined]
async def elicitation_handler(
message, response_type, params: ElicitRequestParams, ctx
):
assert params.requestedSchema == {"type": "object", "properties": {}}
assert response_type is None
return ElicitResult(action="accept")
async with Client(mcp, elicitation_handler=elicitation_handler) as client:
result = await client.call_tool("my_tool", {})
assert result.data is None
async def test_elicitation_empty_response(self):
"""Test elicitation with empty response type."""
mcp = FastMCP("TestServer")
@mcp.tool
async def my_tool(context: Context) -> None:
result = await context.elicit(message="", response_type=None)
return result.data # type: ignore[attr-defined]
async def elicitation_handler(
message, response_type, params: ElicitRequestParams, ctx
):
return ElicitResult(action="accept", content={})
async with Client(mcp, elicitation_handler=elicitation_handler) as client:
result = await client.call_tool("my_tool", {})
assert result.data is None
async def test_elicitation_response_when_no_response_requested(self):
"""Test elicitation with no response type."""
mcp = FastMCP("TestServer")
@mcp.tool
async def my_tool(context: Context) -> None:
result = await context.elicit(message="", response_type=None)
return result.data # type: ignore[attr-defined]
async def elicitation_handler(message, response_type, params, ctx):
return ElicitResult(action="accept", content={"value": "hello"})
async with Client(mcp, elicitation_handler=elicitation_handler) as client:
with pytest.raises(
ToolError, match="Elicitation expected an empty response"
):
await client.call_tool("my_tool", {})
async def test_elicitation_str_response(self):
"""Test elicitation with string schema."""
mcp = FastMCP("TestServer")
@mcp.tool
async def my_tool(context: Context) -> str:
result = await context.elicit(message="", response_type=str)
return result.data # type: ignore[attr-defined]
async def elicitation_handler(message, response_type, params, ctx):
return ElicitResult(action="accept", content={"value": "hello"})
async with Client(mcp, elicitation_handler=elicitation_handler) as client:
result = await client.call_tool("my_tool", {})
assert result.data == "hello"
async def test_elicitation_int_response(self):
"""Test elicitation with number schema."""
mcp = FastMCP("TestServer")
@mcp.tool
async def my_tool(context: Context) -> int:
result = await context.elicit(message="", response_type=int)
return result.data # type: ignore[attr-defined]
async def elicitation_handler(message, response_type, params, ctx):
return ElicitResult(action="accept", content={"value": 42})
async with Client(mcp, elicitation_handler=elicitation_handler) as client:
result = await client.call_tool("my_tool", {})
assert result.data == 42
async def test_elicitation_float_response(self):
"""Test elicitation with number schema."""
mcp = FastMCP("TestServer")
@mcp.tool
async def my_tool(context: Context) -> float:
result = await context.elicit(message="", response_type=float)
return result.data # type: ignore[attr-defined]
async def elicitation_handler(message, response_type, params, ctx):
return ElicitResult(action="accept", content={"value": 3.14})
async with Client(mcp, elicitation_handler=elicitation_handler) as client:
result = await client.call_tool("my_tool", {})
assert result.data == 3.14
async def test_elicitation_bool_response(self):
"""Test elicitation with boolean schema."""
mcp = FastMCP("TestServer")
@mcp.tool
async def my_tool(context: Context) -> bool:
result = await context.elicit(message="", response_type=bool)
return result.data # type: ignore[attr-defined]
async def elicitation_handler(message, response_type, params, ctx):
return ElicitResult(action="accept", content={"value": True})
async with Client(mcp, elicitation_handler=elicitation_handler) as client:
result = await client.call_tool("my_tool", {})
assert result.data is True
async def test_elicitation_literal_response(self):
"""Test elicitation with literal schema."""
mcp = FastMCP("TestServer")
@mcp.tool
async def my_tool(context: Context) -> Literal["x", "y"]:
result = await context.elicit(message="", response_type=Literal["x", "y"]) # type: ignore
return result.data # type: ignore[attr-defined]
async def elicitation_handler(message, response_type, params, ctx):
return ElicitResult(action="accept", content={"value": "x"})
async with Client(mcp, elicitation_handler=elicitation_handler) as client:
result = await client.call_tool("my_tool", {})
assert result.data == "x"
async def test_elicitation_enum_response(self):
"""Test elicitation with enum schema."""
mcp = FastMCP("TestServer")
class ResponseEnum(Enum):
X = "x"
Y = "y"
@mcp.tool
async def my_tool(context: Context) -> ResponseEnum:
result = await context.elicit(message="", response_type=ResponseEnum)
return result.data # type: ignore[attr-defined]
async def elicitation_handler(message, response_type, params, ctx):
return ElicitResult(action="accept", content={"value": "x"})
async with Client(mcp, elicitation_handler=elicitation_handler) as client:
result = await client.call_tool("my_tool", {})
assert result.data == "x"
async def test_elicitation_list_of_strings_response(self):
"""Test elicitation with list schema."""
mcp = FastMCP("TestServer")
@mcp.tool
async def my_tool(context: Context) -> str:
result = await context.elicit(message="", response_type=["x", "y"])
return result.data # type: ignore[attr-defined]
async def elicitation_handler(message, response_type, params, ctx):
return ElicitResult(action="accept", content={"value": "x"})
async with Client(mcp, elicitation_handler=elicitation_handler) as client:
result = await client.call_tool("my_tool", {})
assert result.data == "x"
async def test_elicitation_handler_error():
"""Test error handling in elicitation handler."""
mcp = FastMCP("TestServer")
@mcp.tool
async def failing_elicit(context: Context) -> str:
try:
result = await context.elicit(message="This will fail", response_type=str)
assert isinstance(result, AcceptedElicitation)
assert result.action == "accept"
return f"Got: {result.data}"
except Exception as e:
return f"Error: {str(e)}"
async def elicitation_handler(message, response_type, params, ctx):
raise ValueError("Handler failed!")
async with Client(mcp, elicitation_handler=elicitation_handler) as client:
result = await client.call_tool("failing_elicit", {})
assert "Error:" in result.data
async def test_elicitation_multiple_calls():
"""Test multiple elicitation calls in sequence."""
mcp = FastMCP("TestServer")
@mcp.tool
async def multi_step_form(context: Context) -> str:
# First question
name_result = await context.elicit(
message="What's your name?", response_type=str
)
assert isinstance(name_result, AcceptedElicitation)
if name_result.action != "accept":
return "Form abandoned"
# Second question
age_result = await context.elicit(message="What's your age?", response_type=int)
assert isinstance(age_result, AcceptedElicitation)
if age_result.action != "accept":
return f"Hello {name_result.data}, form incomplete"
return f"Hello {name_result.data}, you are {age_result.data} years old"
call_count = 0
async def elicitation_handler(message, response_type, params, ctx):
nonlocal call_count
call_count += 1
if call_count == 1:
return ElicitResult(action="accept", content={"value": "Bob"})
elif call_count == 2:
return ElicitResult(action="accept", content={"value": 25})
else:
raise ValueError("Unexpected call")
async with Client(mcp, elicitation_handler=elicitation_handler) as client:
result = await client.call_tool("multi_step_form", {})
assert result.data == "Hello Bob, you are 25 years old"
assert call_count == 2
@dataclass
class UserInfo:
name: str
age: int
class UserInfoTypedDict(TypedDict):
name: str
age: int
class UserInfoPydantic(BaseModel):
name: str
age: int
@pytest.mark.parametrize(
"structured_type", [UserInfo, UserInfoTypedDict, UserInfoPydantic]
)
async def test_structured_response_type(
structured_type: type[UserInfo | UserInfoTypedDict | UserInfoPydantic],
):
"""Test elicitation with dataclass response type."""
mcp = FastMCP("TestServer")
@mcp.tool
async def get_user_info(context: Context) -> str:
result = await context.elicit(
message="Please provide your information", response_type=structured_type
)
assert isinstance(result, AcceptedElicitation)
if result.action == "accept":
if isinstance(result.data, dict):
return f"User: {result.data['name']}, age: {result.data['age']}" # type: ignore[index]
else:
return f"User: {result.data.name}, age: {result.data.age}" # type: ignore[attr-defined]
return "No user info provided"
async def elicitation_handler(message, response_type, params, ctx):
# Verify we get the dataclass type
assert (
TypeAdapter(response_type).json_schema()
== TypeAdapter(structured_type).json_schema()
)
# Verify the schema has the dataclass fields (available in params)
schema = params.requestedSchema
assert schema["type"] == "object"
assert "name" in schema["properties"]
assert "age" in schema["properties"]
assert schema["properties"]["name"]["type"] == "string"
assert schema["properties"]["age"]["type"] == "integer"
return ElicitResult(action="accept", content=UserInfo(name="Alice", age=30))
async with Client(mcp, elicitation_handler=elicitation_handler) as client:
result = await client.call_tool("get_user_info", {})
assert result.data == "User: Alice, age: 30"
async def test_all_primitive_field_types():
class DataEnum(Enum):
X = "x"
Y = "y"
@dataclass
class Data:
integer: int
float_: float
number: int | float
boolean: bool
string: str
constant: Literal["x"]
union: Literal["x"] | Literal["y"]
choice: Literal["x", "y"]
enum: DataEnum
mcp = FastMCP("TestServer")
@mcp.tool
async def get_data(context: Context) -> Data:
result = await context.elicit(message="Enter data", response_type=Data)
return result.data # type: ignore[attr-defined]
async def elicitation_handler(message, response_type, params, ctx):
return ElicitResult(
action="accept",
content=Data(
integer=1,
float_=1.0,
number=1.0,
boolean=True,
string="hello",
constant="x",
union="x",
choice="x",
enum=DataEnum.X,
),
)
async with Client(mcp, elicitation_handler=elicitation_handler) as client:
result = await client.call_tool("get_data", {})
# Now all literal/enum fields should be preserved as strings
result_data = asdict(result.data)
result_data_enum = result_data.pop("enum")
assert result_data_enum == "x" # Should be a string now, not an enum
assert result_data == {
"integer": 1,
"float_": 1.0,
"number": 1.0,
"boolean": True,
"string": "hello",
"constant": "x",
"union": "x",
"choice": "x",
}
class TestValidation:
async def test_schema_validation_rejects_non_object(self):
"""Test that non-object schemas are rejected."""
with pytest.raises(TypeError, match="must be an object schema"):
validate_elicitation_json_schema({"type": "string"})
async def test_schema_validation_rejects_nested_objects(self):
"""Test that nested object schemas are rejected."""
with pytest.raises(
TypeError, match="has type 'object' which is not a primitive type"
):
validate_elicitation_json_schema(
{
"type": "object",
"properties": {
"user": {
"type": "object",
"properties": {"name": {"type": "string"}},
}
},
}
)
async def test_schema_validation_rejects_arrays(self):
"""Test that array schemas are rejected."""
with pytest.raises(
TypeError, match="has type 'array' which is not a primitive type"
):
validate_elicitation_json_schema(
{
"type": "object",
"properties": {
"users": {"type": "array", "items": {"type": "string"}}
},
}
)
class TestPatternMatching:
async def test_pattern_matching_accept(self):
"""Test pattern matching with AcceptedElicitation."""
mcp = FastMCP("TestServer")
@mcp.tool
async def pattern_match_tool(context: Context) -> str:
result = await context.elicit("Enter your name:", response_type=str)
match result:
case AcceptedElicitation(data=name):
return f"Hello {name}!"
case DeclinedElicitation():
return "You declined"
case CancelledElicitation():
return "Cancelled"
case _:
return "Unknown result"
async def elicitation_handler(message, response_type, params, ctx):
return ElicitResult(action="accept", content={"value": "Alice"})
async with Client(mcp, elicitation_handler=elicitation_handler) as client:
result = await client.call_tool("pattern_match_tool", {})
assert result.data == "Hello Alice!"
async def test_pattern_matching_decline(self):
"""Test pattern matching with DeclinedElicitation."""
mcp = FastMCP("TestServer")
@mcp.tool
async def pattern_match_tool(context: Context) -> str:
result = await context.elicit("Enter your name:", response_type=str)
match result:
case AcceptedElicitation(data=name):
return f"Hello {name}!"
case DeclinedElicitation():
return "You declined"
case CancelledElicitation():
return "Cancelled"
case _:
return "Unknown result"
async def elicitation_handler(message, response_type, params, ctx):
return ElicitResult(action="decline")
async with Client(mcp, elicitation_handler=elicitation_handler) as client:
result = await client.call_tool("pattern_match_tool", {})
assert result.data == "You declined"
async def test_pattern_matching_cancel(self):
"""Test pattern matching with CancelledElicitation."""
mcp = FastMCP("TestServer")
@mcp.tool
async def pattern_match_tool(context: Context) -> str:
result = await context.elicit("Enter your name:", response_type=str)
match result:
case AcceptedElicitation(data=name):
return f"Hello {name}!"
case DeclinedElicitation():
return "You declined"
case CancelledElicitation():
return "Cancelled"
case _:
return "Unknown result"
async def elicitation_handler(message, response_type, params, ctx):
return ElicitResult(action="cancel")
async with Client(mcp, elicitation_handler=elicitation_handler) as client:
result = await client.call_tool("pattern_match_tool", {})
assert result.data == "Cancelled"
async def test_elicitation_implicit_acceptance(fastmcp_server):
"""Test that elicitation handler can return data directly without ElicitResult wrapper."""
async def elicitation_handler(message, response_type, params, ctx):
# Return data directly without wrapping in ElicitResult
# This should be treated as implicit acceptance
return response_type(name="Bob")
async with Client(
fastmcp_server, elicitation_handler=elicitation_handler
) as client:
result = await client.call_tool("ask_for_name")
assert result.data == "Hello, Bob!"
async def test_elicitation_implicit_acceptance_must_be_dict(fastmcp_server):
"""Test that elicitation handler can return data directly without ElicitResult wrapper."""
async def elicitation_handler(message, response_type, params, ctx):
# Return data directly without wrapping in ElicitResult
# This should be treated as implicit acceptance
return "Bob"
async with Client(
fastmcp_server, elicitation_handler=elicitation_handler
) as client:
with pytest.raises(
ToolError,
match="Elicitation responses must be serializable as a JSON object",
):
await client.call_tool("ask_for_name")
def test_enum_elicitation_schema_inline():
"""Test that enum schemas are generated inline without $ref/$defs for MCP compatibility."""
class Priority(Enum):
LOW = "low"
MEDIUM = "medium"
HIGH = "high"
@dataclass
class TaskRequest:
title: str
priority: Priority
# Generate elicitation schema
schema = get_elicitation_schema(TaskRequest)
# Verify no $defs section exists (enums should be inlined)
assert "$defs" not in schema, (
"Schema should not contain $defs - enums must be inline"
)
# Verify no $ref in properties
for prop_name, prop_schema in schema.get("properties", {}).items():
assert "$ref" not in prop_schema, (
f"Property {prop_name} contains $ref - should be inline"
)
# Verify the priority field has inline enum values
priority_schema = schema["properties"]["priority"]
assert "enum" in priority_schema, "Priority should have enum values inline"
assert priority_schema["enum"] == ["low", "medium", "high"]
assert priority_schema.get("type") == "string"
# Verify title field is a simple string
assert schema["properties"]["title"]["type"] == "string"
def test_enum_elicitation_schema_with_enum_names():
"""Test that enum schemas can include enumNames for better UI display."""
class TaskStatus(Enum):
NOT_STARTED = "not_started"
IN_PROGRESS = "in_progress"
COMPLETED = "completed"
ON_HOLD = "on_hold"
@dataclass
class TaskUpdate:
task_id: str
status: TaskStatus
# Generate elicitation schema
schema = get_elicitation_schema(TaskUpdate)
# Verify enum is inline
assert "$defs" not in schema
assert "$ref" not in str(schema)
status_schema = schema["properties"]["status"]
assert "enum" in status_schema
assert status_schema["enum"] == [
"not_started",
"in_progress",
"completed",
"on_hold",
]
# Check if enumNames were added for display
assert "enumNames" in status_schema
assert status_schema["enumNames"] == [
"Not Started",
"In Progress",
"Completed",
"On Hold",
]
class TestElicitationDefaults:
"""Test suite for default values in elicitation schemas."""
def test_string_default_preserved(self):
"""Test that string defaults are preserved in the schema."""
class Model(BaseModel):
email: str = Field(default="[email protected]")
schema = get_elicitation_schema(Model)
props = schema.get("properties", {})
assert "email" in props
assert "default" in props["email"]
assert props["email"]["default"] == "[email protected]"
assert props["email"]["type"] == "string"
def test_integer_default_preserved(self):
"""Test that integer defaults are preserved in the schema."""
class Model(BaseModel):
count: int = Field(default=50)
schema = get_elicitation_schema(Model)
props = schema.get("properties", {})
assert "count" in props
assert "default" in props["count"]
assert props["count"]["default"] == 50
assert props["count"]["type"] == "integer"
def test_number_default_preserved(self):
"""Test that number defaults are preserved in the schema."""
class Model(BaseModel):
price: float = Field(default=3.14)
schema = get_elicitation_schema(Model)
props = schema.get("properties", {})
assert "price" in props
assert "default" in props["price"]
assert props["price"]["default"] == 3.14
assert props["price"]["type"] == "number"
def test_boolean_default_preserved(self):
"""Test that boolean defaults are preserved in the schema."""
class Model(BaseModel):
enabled: bool = Field(default=False)
schema = get_elicitation_schema(Model)
props = schema.get("properties", {})
assert "enabled" in props
assert "default" in props["enabled"]
assert props["enabled"]["default"] is False
assert props["enabled"]["type"] == "boolean"
def test_enum_default_preserved(self):
"""Test that enum defaults are preserved in the schema."""
class Priority(Enum):
LOW = "low"
MEDIUM = "medium"
HIGH = "high"
class Model(BaseModel):
choice: Priority = Field(default=Priority.MEDIUM)
schema = get_elicitation_schema(Model)
props = schema.get("properties", {})
assert "choice" in props
assert "default" in props["choice"]
assert props["choice"]["default"] == "medium"
assert "enum" in props["choice"]
assert props["choice"]["type"] == "string"
def test_all_defaults_preserved_together(self):
"""Test that all default types are preserved when used together."""
class Priority(Enum):
A = "A"
B = "B"
class Model(BaseModel):
string_field: str = Field(default="[email protected]")
integer_field: int = Field(default=50)
number_field: float = Field(default=3.14)
boolean_field: bool = Field(default=False)
enum_field: Priority = Field(default=Priority.A)
schema = get_elicitation_schema(Model)
props = schema.get("properties", {})
assert props["string_field"]["default"] == "[email protected]"
assert props["integer_field"]["default"] == 50
assert props["number_field"]["default"] == 3.14
assert props["boolean_field"]["default"] is False
assert props["enum_field"]["default"] == "A"
def test_mixed_defaults_and_required(self):
"""Test that fields with defaults are not in required list."""
class Model(BaseModel):
required_field: str = Field(description="Required field")
optional_with_default: int = Field(default=42)
schema = get_elicitation_schema(Model)
props = schema.get("properties", {})
required = schema.get("required", [])
assert "required_field" in required
assert "optional_with_default" not in required
assert props["optional_with_default"]["default"] == 42
def test_compress_schema_preserves_defaults(self):
"""Test that compress_schema() doesn't strip default values."""
class Model(BaseModel):
string_field: str = Field(default="test")
integer_field: int = Field(default=42)
schema = get_elicitation_schema(Model)
props = schema.get("properties", {})
assert "default" in props["string_field"]
assert "default" in props["integer_field"]