"""
Test the elicitation feature using stdio transport.
"""
import pytest
from pydantic import BaseModel, Field
from mcp.server.fastmcp import Context, FastMCP
from mcp.shared.memory import create_connected_server_and_client_session
from mcp.types import ElicitResult, TextContent
# Shared schema for basic tests
class AnswerSchema(BaseModel):
answer: str = Field(description="The user's answer to the question")
def create_ask_user_tool(mcp: FastMCP):
"""Create a standard ask_user tool that handles all elicitation responses."""
@mcp.tool(description="A tool that uses elicitation")
async def ask_user(prompt: str, ctx: Context) -> str:
result = await ctx.elicit(
message=f"Tool wants to ask: {prompt}",
schema=AnswerSchema,
)
if result.action == "accept" and result.data:
return f"User answered: {result.data.answer}"
elif result.action == "decline":
return "User declined to answer"
else:
return "User cancelled"
return ask_user
async def call_tool_and_assert(
mcp: FastMCP,
elicitation_callback,
tool_name: str,
args: dict,
expected_text: str | None = None,
text_contains: list[str] | None = None,
):
"""Helper to create session, call tool, and assert result."""
async with create_connected_server_and_client_session(
mcp._mcp_server, elicitation_callback=elicitation_callback
) as client_session:
await client_session.initialize()
result = await client_session.call_tool(tool_name, args)
assert len(result.content) == 1
assert isinstance(result.content[0], TextContent)
if expected_text is not None:
assert result.content[0].text == expected_text
elif text_contains is not None:
for substring in text_contains:
assert substring in result.content[0].text
return result
@pytest.mark.anyio
async def test_stdio_elicitation():
"""Test the elicitation feature using stdio transport."""
mcp = FastMCP(name="StdioElicitationServer")
create_ask_user_tool(mcp)
# Create a custom handler for elicitation requests
async def elicitation_callback(context, params):
if params.message == "Tool wants to ask: What is your name?":
return ElicitResult(action="accept", content={"answer": "Test User"})
else:
raise ValueError(f"Unexpected elicitation message: {params.message}")
await call_tool_and_assert(
mcp, elicitation_callback, "ask_user", {"prompt": "What is your name?"}, "User answered: Test User"
)
@pytest.mark.anyio
async def test_stdio_elicitation_decline():
"""Test elicitation with user declining."""
mcp = FastMCP(name="StdioElicitationDeclineServer")
create_ask_user_tool(mcp)
async def elicitation_callback(context, params):
return ElicitResult(action="decline")
await call_tool_and_assert(
mcp, elicitation_callback, "ask_user", {"prompt": "What is your name?"}, "User declined to answer"
)
@pytest.mark.anyio
async def test_elicitation_schema_validation():
"""Test that elicitation schemas must only contain primitive types."""
mcp = FastMCP(name="ValidationTestServer")
def create_validation_tool(name: str, schema_class: type[BaseModel]):
@mcp.tool(name=name, description=f"Tool testing {name}")
async def tool(ctx: Context) -> str:
try:
await ctx.elicit(message="This should fail validation", schema=schema_class)
return "Should not reach here"
except TypeError as e:
return f"Validation failed as expected: {str(e)}"
return tool
# Test cases for invalid schemas
class InvalidListSchema(BaseModel):
names: list[str] = Field(description="List of names")
class NestedModel(BaseModel):
value: str
class InvalidNestedSchema(BaseModel):
nested: NestedModel = Field(description="Nested model")
create_validation_tool("invalid_list", InvalidListSchema)
create_validation_tool("nested_model", InvalidNestedSchema)
# Dummy callback (won't be called due to validation failure)
async def elicitation_callback(context, params):
return ElicitResult(action="accept", content={})
async with create_connected_server_and_client_session(
mcp._mcp_server, elicitation_callback=elicitation_callback
) as client_session:
await client_session.initialize()
# Test both invalid schemas
for tool_name, field_name in [("invalid_list", "names"), ("nested_model", "nested")]:
result = await client_session.call_tool(tool_name, {})
assert len(result.content) == 1
assert isinstance(result.content[0], TextContent)
assert "Validation failed as expected" in result.content[0].text
assert field_name in result.content[0].text
@pytest.mark.anyio
async def test_elicitation_with_optional_fields():
"""Test that Optional fields work correctly in elicitation schemas."""
mcp = FastMCP(name="OptionalFieldServer")
class OptionalSchema(BaseModel):
required_name: str = Field(description="Your name (required)")
optional_age: int | None = Field(default=None, description="Your age (optional)")
optional_email: str | None = Field(default=None, description="Your email (optional)")
subscribe: bool | None = Field(default=False, description="Subscribe to newsletter?")
@mcp.tool(description="Tool with optional fields")
async def optional_tool(ctx: Context) -> str:
result = await ctx.elicit(message="Please provide your information", schema=OptionalSchema)
if result.action == "accept" and result.data:
info = [f"Name: {result.data.required_name}"]
if result.data.optional_age is not None:
info.append(f"Age: {result.data.optional_age}")
if result.data.optional_email is not None:
info.append(f"Email: {result.data.optional_email}")
info.append(f"Subscribe: {result.data.subscribe}")
return ", ".join(info)
else:
return f"User {result.action}"
# Test cases with different field combinations
test_cases = [
(
# All fields provided
{"required_name": "John Doe", "optional_age": 30, "optional_email": "john@example.com", "subscribe": True},
"Name: John Doe, Age: 30, Email: john@example.com, Subscribe: True",
),
(
# Only required fields
{"required_name": "Jane Smith"},
"Name: Jane Smith, Subscribe: False",
),
]
for content, expected in test_cases:
async def callback(context, params):
return ElicitResult(action="accept", content=content)
await call_tool_and_assert(mcp, callback, "optional_tool", {}, expected)
# Test invalid optional field
class InvalidOptionalSchema(BaseModel):
name: str = Field(description="Name")
optional_list: list[str] | None = Field(default=None, description="Invalid optional list")
@mcp.tool(description="Tool with invalid optional field")
async def invalid_optional_tool(ctx: Context) -> str:
try:
await ctx.elicit(message="This should fail", schema=InvalidOptionalSchema)
return "Should not reach here"
except TypeError as e:
return f"Validation failed: {str(e)}"
await call_tool_and_assert(
mcp,
lambda c, p: ElicitResult(action="accept", content={}),
"invalid_optional_tool",
{},
text_contains=["Validation failed:", "optional_list"],
)
