fastmcp/tests/tools/test_tool.py
2025-06-16 08:10:34 +02:00

720 lines
27 KiB
Python

import pytest
from mcp.types import (
AudioContent,
EmbeddedResource,
ImageContent,
TextContent,
TextResourceContents,
)
from pydantic import AnyUrl, BaseModel
from fastmcp import FastMCP
from fastmcp.client import Client
from fastmcp.exceptions import ToolError
from fastmcp.tools.tool import Tool, _convert_to_content
from fastmcp.utilities.tests import temporary_settings
from fastmcp.utilities.types import Audio, File, Image
class TestToolFromFunction:
def test_basic_function(self):
"""Test registering and running a basic function."""
def add(a: int, b: int) -> int:
"""Add two numbers."""
return a + b
tool = Tool.from_function(add)
assert tool.name == "add"
assert tool.description == "Add two numbers."
assert len(tool.parameters["properties"]) == 2
assert tool.parameters["properties"]["a"]["type"] == "integer"
assert tool.parameters["properties"]["b"]["type"] == "integer"
async def test_async_function(self):
"""Test registering and running an async function."""
async def fetch_data(url: str) -> str:
"""Fetch data from URL."""
return f"Data from {url}"
tool = Tool.from_function(fetch_data)
assert tool.name == "fetch_data"
assert tool.description == "Fetch data from URL."
assert tool.parameters["properties"]["url"]["type"] == "string"
def test_callable_object(self):
class Adder:
"""Adds two numbers."""
def __call__(self, x: int, y: int) -> int:
"""ignore this"""
return x + y
tool = Tool.from_function(Adder())
assert tool.name == "Adder"
assert tool.description == "Adds two numbers."
assert len(tool.parameters["properties"]) == 2
assert tool.parameters["properties"]["x"]["type"] == "integer"
assert tool.parameters["properties"]["y"]["type"] == "integer"
def test_async_callable_object(self):
class Adder:
"""Adds two numbers."""
async def __call__(self, x: int, y: int) -> int:
"""ignore this"""
return x + y
tool = Tool.from_function(Adder())
assert tool.name == "Adder"
assert tool.description == "Adds two numbers."
assert len(tool.parameters["properties"]) == 2
assert tool.parameters["properties"]["x"]["type"] == "integer"
assert tool.parameters["properties"]["y"]["type"] == "integer"
def test_pydantic_model_function(self):
"""Test registering a function that takes a Pydantic model."""
class UserInput(BaseModel):
name: str
age: int
def create_user(user: UserInput, flag: bool) -> dict:
"""Create a new user."""
return {"id": 1, **user.model_dump()}
tool = Tool.from_function(create_user)
assert tool.name == "create_user"
assert tool.description == "Create a new user."
assert "name" in tool.parameters["$defs"]["UserInput"]["properties"]
assert "age" in tool.parameters["$defs"]["UserInput"]["properties"]
assert "flag" in tool.parameters["properties"]
async def test_tool_with_image_return(self):
def image_tool(data: bytes) -> Image:
return Image(data=data)
tool = Tool.from_function(image_tool)
result = await tool.run({"data": "test.png"})
assert tool.parameters["properties"]["data"]["type"] == "string"
assert isinstance(result[0], ImageContent)
async def test_tool_with_audio_return(self):
def audio_tool(data: bytes) -> Audio:
return Audio(data=data)
tool = Tool.from_function(audio_tool)
result = await tool.run({"data": "test.wav"})
assert tool.parameters["properties"]["data"]["type"] == "string"
assert isinstance(result[0], AudioContent)
async def test_tool_with_file_return(self):
def file_tool(data: bytes) -> File:
return File(data=data, format="octet-stream")
tool = Tool.from_function(file_tool)
result = await tool.run({"data": "test.bin"})
assert tool.parameters["properties"]["data"]["type"] == "string"
assert len(result) == 1
assert isinstance(result[0], EmbeddedResource)
assert result[0].type == "resource"
assert hasattr(result[0], "resource")
resource = result[0].resource
assert resource.mimeType == "application/octet-stream"
def test_non_callable_fn(self):
with pytest.raises(TypeError, match="not a callable object"):
Tool.from_function(1) # type: ignore
def test_lambda(self):
tool = Tool.from_function(lambda x: x, name="my_tool")
assert tool.name == "my_tool"
def test_lambda_with_no_name(self):
with pytest.raises(
ValueError, match="You must provide a name for lambda functions"
):
Tool.from_function(lambda x: x)
def test_private_arguments(self):
def add(_a: int, _b: int) -> int:
"""Add two numbers."""
return _a + _b
tool = Tool.from_function(add)
assert tool.parameters["properties"]["_a"]["type"] == "integer"
assert tool.parameters["properties"]["_b"]["type"] == "integer"
def test_tool_with_varargs_not_allowed(self):
def func(a: int, b: int, *args: int) -> int:
"""Add two numbers."""
return a + b
with pytest.raises(
ValueError, match=r"Functions with \*args are not supported as tools"
):
Tool.from_function(func)
def test_tool_with_varkwargs_not_allowed(self):
def func(a: int, b: int, **kwargs: int) -> int:
"""Add two numbers."""
return a + b
with pytest.raises(
ValueError, match=r"Functions with \*\*kwargs are not supported as tools"
):
Tool.from_function(func)
async def test_instance_method(self):
class MyClass:
def add(self, x: int, y: int) -> int:
"""Add two numbers."""
return x + y
obj = MyClass()
tool = Tool.from_function(obj.add)
assert tool.name == "add"
assert tool.description == "Add two numbers."
assert "self" not in tool.parameters["properties"]
async def test_instance_method_with_varargs_not_allowed(self):
class MyClass:
def add(self, x: int, y: int, *args: int) -> int:
"""Add two numbers."""
return x + y
obj = MyClass()
with pytest.raises(
ValueError, match=r"Functions with \*args are not supported as tools"
):
Tool.from_function(obj.add)
async def test_instance_method_with_varkwargs_not_allowed(self):
class MyClass:
def add(self, x: int, y: int, **kwargs: int) -> int:
"""Add two numbers."""
return x + y
obj = MyClass()
with pytest.raises(
ValueError, match=r"Functions with \*\*kwargs are not supported as tools"
):
Tool.from_function(obj.add)
async def test_classmethod(self):
class MyClass:
x: int = 10
@classmethod
def call(cls, x: int, y: int) -> int:
"""Add two numbers."""
return x + y
tool = Tool.from_function(MyClass.call)
assert tool.name == "call"
assert tool.description == "Add two numbers."
assert "x" in tool.parameters["properties"]
assert "y" in tool.parameters["properties"]
async def test_tool_serializer(self):
"""Test that a tool's serializer is used to serialize the result."""
def custom_serializer(data) -> str:
return f"Custom serializer: {data}"
def process_list(items: list[int]) -> int:
return sum(items)
tool = Tool.from_function(process_list, serializer=custom_serializer)
result = await tool.run(arguments={"items": [1, 2, 3, 4, 5]})
assert isinstance(result[0], TextContent)
assert result[0].text == "Custom serializer: 15"
class TestLegacyToolJsonParsing:
"""Tests for Tool's JSON pre-parsing functionality."""
@pytest.fixture(autouse=True)
def enable_legacy_json_parsing(self):
with temporary_settings(tool_attempt_parse_json_args=True):
yield
async def test_json_string_arguments(self):
"""Test that JSON string arguments are parsed and validated correctly"""
def simple_func(x: int, y: list[str]) -> str:
return f"{x}-{','.join(y)}"
# Create a tool to use its JSON pre-parsing logic
tool = Tool.from_function(simple_func)
# Prepare arguments where some are JSON strings
json_args = {
"x": 1,
"y": '["a", "b", "c"]', # JSON string
}
# Run the tool which will do JSON parsing
result = await tool.run(json_args)
assert result[0].text == "1-a,b,c" # type: ignore[attr-dict]
async def test_str_vs_list_str(self):
"""Test handling of string vs list[str] type annotations."""
def func_with_str_types(str_or_list: str | list[str]) -> str | list[str]:
return str_or_list
tool = Tool.from_function(func_with_str_types)
# Test regular string input (should remain a string)
result = await tool.run({"str_or_list": "hello"})
assert result[0].text == "hello" # type: ignore[attr-dict]
# Test JSON string input (should be parsed as a string)
result = await tool.run({"str_or_list": '"hello"'})
assert result[0].text == "hello" # type: ignore[attr-dict]
# Test JSON list input (should be parsed as a list)
result = await tool.run({"str_or_list": '["hello", "world"]'})
# The exact formatting might vary, so we just check that it contains the key elements
text_without_whitespace = result[0].text.replace(" ", "").replace("\n", "") # type: ignore[attr-dict]
assert "hello" in text_without_whitespace
assert "world" in text_without_whitespace
assert "[" in text_without_whitespace
assert "]" in text_without_whitespace
async def test_keep_str_as_str(self):
"""Test that string arguments are kept as strings when they're not valid JSON"""
def func_with_str_types(string: str) -> str:
return string
tool = Tool.from_function(func_with_str_types)
# Invalid JSON should remain a string
invalid_json = "{'nice to meet you': 'hello', 'goodbye': 5}"
result = await tool.run({"string": invalid_json})
assert result[0].text == invalid_json # type: ignore[attr-dict]
async def test_keep_str_union_as_str(self):
"""Test that string arguments are kept as strings when parsing would create an invalid value"""
def func_with_str_types(
string: str | dict[int, str] | None,
) -> str | dict[int, str] | None:
return string
tool = Tool.from_function(func_with_str_types)
# Invalid JSON for the union type should remain a string
invalid_json = "{'nice to meet you': 'hello', 'goodbye': 5}"
result = await tool.run({"string": invalid_json})
assert result[0].text == invalid_json # type: ignore[attr-dict]
async def test_complex_type_validation(self):
"""Test that parsed JSON is validated against complex types"""
class SomeModel(BaseModel):
x: int
y: dict[int, str]
def func_with_complex_type(data: SomeModel) -> SomeModel:
return data
tool = Tool.from_function(func_with_complex_type)
# Valid JSON for the model
valid_json = '{"x": 1, "y": {"1": "hello"}}'
result = await tool.run({"data": valid_json})
assert '"x": 1' in result[0].text # type: ignore[attr-dict]
assert '"y": {' in result[0].text # type: ignore[attr-dict]
assert '"1": "hello"' in result[0].text # type: ignore[attr-dict]
# Invalid JSON for the model (y has string keys, not int keys)
# Should throw a validation error
invalid_json = '{"x": 1, "y": {"invalid": "hello"}}'
with pytest.raises(Exception):
await tool.run({"data": invalid_json})
async def test_tool_list_coercion(self):
"""Test JSON string to collection type coercion."""
mcp = FastMCP()
@mcp.tool
def process_list(items: list[int]) -> int:
return sum(items)
async with Client(mcp) as client:
# JSON array string should be coerced to list
result = await client.call_tool(
"process_list", {"items": "[1, 2, 3, 4, 5]"}
)
assert result[0].text == "15" # type: ignore[attr-dict]
async def test_tool_list_coercion_error(self):
"""Test that a list coercion error is raised if the input is not a valid list."""
mcp = FastMCP()
@mcp.tool
def process_list(items: list[int]) -> int:
return sum(items)
async with Client(mcp) as client:
with pytest.raises(
ToolError,
match="Error calling tool 'process_list'",
):
await client.call_tool("process_list", {"items": "['a', 'b', 3]"})
async def test_tool_dict_coercion(self):
"""Test JSON string to dict type coercion."""
mcp = FastMCP()
@mcp.tool
def process_dict(data: dict[str, int]) -> int:
return sum(data.values())
async with Client(mcp) as client:
# JSON object string should be coerced to dict
result = await client.call_tool(
"process_dict", {"data": '{"a": 1, "b": "2", "c": 3}'}
)
assert result[0].text == "6" # type: ignore[attr-dict]
async def test_tool_set_coercion(self):
"""Test JSON string to set type coercion."""
mcp = FastMCP()
@mcp.tool
def process_set(items: set[int]) -> int:
assert isinstance(items, set)
return sum(items)
async with Client(mcp) as client:
result = await client.call_tool("process_set", {"items": "[1, 2, 3, 4, 5]"})
assert result[0].text == "15" # type: ignore[attr-dict]
async def test_tool_tuple_coercion(self):
"""Test JSON string to tuple type coercion."""
mcp = FastMCP()
@mcp.tool
def process_tuple(items: tuple[int, str]) -> int:
assert isinstance(items, tuple)
return items[0] + len(items[1])
async with Client(mcp) as client:
result = await client.call_tool("process_tuple", {"items": '["1", "two"]'})
assert isinstance(result[0], TextContent)
assert result[0].text == "4" # type: ignore[attr-dict]
class TestConvertResultToContent:
"""Tests for the _convert_to_content helper function."""
def test_none_result(self):
"""Test that None results in an empty list."""
result = _convert_to_content(None)
assert isinstance(result, list)
assert len(result) == 0
def test_text_content_result(self):
"""Test that TextContent is returned as a list containing itself."""
content = TextContent(type="text", text="hello")
result = _convert_to_content(content)
assert isinstance(result, list)
assert len(result) == 1
assert result[0] is content
def test_image_content_result(self):
"""Test that ImageContent is returned as a list containing itself."""
content = ImageContent(type="image", data="fakeimagedata", mimeType="image/png")
result = _convert_to_content(content)
assert isinstance(result, list)
assert len(result) == 1
assert result[0] is content
def test_embedded_resource_result(self):
"""Test that EmbeddedResource is returned as a list containing itself."""
content = EmbeddedResource(
type="resource",
resource=TextResourceContents(
uri=AnyUrl("resource://test"),
mimeType="text/plain",
text="resource content",
),
)
result = _convert_to_content(content)
assert isinstance(result, list)
assert len(result) == 1
assert result[0] is content
def test_image_object_result(self):
"""Test that an Image object is converted to ImageContent."""
image_obj = Image(data=b"fakeimagedata")
result = _convert_to_content(image_obj)
assert isinstance(result, list)
assert len(result) == 1
assert isinstance(result[0], ImageContent)
assert result[0].data == "ZmFrZWltYWdlZGF0YQ=="
def test_audio_object_result(self):
"""Test that an Audio object is converted to AudioContent."""
audio_obj = Audio(data=b"fakeaudiodata")
result = _convert_to_content(audio_obj)
assert isinstance(result, list)
assert len(result) == 1
assert isinstance(result[0], AudioContent)
assert result[0].data == "ZmFrZWF1ZGlvZGF0YQ=="
def test_file_object_result(self):
"""Test that a File object is converted to EmbeddedResource with BlobResourceContents."""
file_obj = File(data=b"filedata", format="octet-stream")
result = _convert_to_content(file_obj)
assert isinstance(result, list)
assert len(result) == 1
assert isinstance(result[0], EmbeddedResource)
assert result[0].type == "resource"
assert hasattr(result[0], "resource")
resource = result[0].resource
assert resource.mimeType == "application/octet-stream"
# Check for blob attribute and its value
assert hasattr(resource, "blob")
assert getattr(resource, "blob") == "ZmlsZWRhdGE=" # base64 encoded "filedata"
# Convert URI to string for startswith check
assert str(resource.uri).startswith("file:///resource.octet-stream")
def test_file_object_text_result(self):
"""Test that a File object with text data is converted to EmbeddedResource with TextResourceContents."""
file_obj = File(data=b"sometext", format="plain")
result = _convert_to_content(file_obj)
assert isinstance(result, list)
assert len(result) == 1
assert isinstance(result[0], EmbeddedResource)
assert result[0].type == "resource"
resource = result[0].resource
assert isinstance(resource, TextResourceContents)
assert resource.mimeType == "text/plain"
assert resource.text == "sometext"
def test_basic_type_result(self):
"""Test that a basic type is converted to TextContent."""
result = _convert_to_content(123)
assert isinstance(result, list)
assert len(result) == 1
assert isinstance(result[0], TextContent)
assert result[0].text == "123"
result = _convert_to_content("hello")
assert isinstance(result, list)
assert len(result) == 1
assert isinstance(result[0], TextContent)
assert result[0].text == "hello"
result = _convert_to_content({"a": 1, "b": 2})
assert isinstance(result, list)
assert len(result) == 1
assert isinstance(result[0], TextContent)
assert result[0].text == '{\n "a": 1,\n "b": 2\n}'
def test_list_of_basic_types(self):
"""Test that a list of basic types is converted to a single TextContent."""
result = _convert_to_content([1, "two", {"c": 3}])
assert isinstance(result, list)
assert len(result) == 1
assert isinstance(result[0], TextContent)
assert result[0].text == '[\n 1,\n "two",\n {\n "c": 3\n }\n]'
def test_list_of_mcp_types(self):
"""Test that a list of MCP types is returned as a list of those types."""
content1 = TextContent(type="text", text="hello")
content2 = ImageContent(
type="image", data="fakeimagedata2", mimeType="image/png"
)
result = _convert_to_content([content1, content2])
assert isinstance(result, list)
assert len(result) == 2
assert result[0] is content1
assert result[1] is content2
def test_list_of_mixed_types(self):
"""Test that a list of mixed types is converted correctly."""
content1 = TextContent(type="text", text="hello")
image_obj = Image(data=b"fakeimagedata")
basic_data = {"a": 1}
result = _convert_to_content([content1, image_obj, basic_data])
assert isinstance(result, list)
assert len(result) == 3
text_content_count = sum(isinstance(item, TextContent) for item in result)
image_content_count = sum(isinstance(item, ImageContent) for item in result)
assert text_content_count == 2
assert image_content_count == 1
text_item = next(item for item in result if isinstance(item, TextContent))
assert text_item.text == '{\n "a": 1\n}'
image_item = next(item for item in result if isinstance(item, ImageContent))
assert image_item.data == "ZmFrZWltYWdlZGF0YQ=="
def test_list_of_mixed_types_list(self):
"""Test that a list of mixed types, including a list as one of the elements, is converted correctly."""
content1 = TextContent(type="text", text="hello")
image_obj = Image(data=b"fakeimagedata")
basic_data = [{"a": 1}, {"b": 2}]
result = _convert_to_content([content1, image_obj, basic_data])
assert isinstance(result, list)
assert len(result) == 3
text_content_count = sum(isinstance(item, TextContent) for item in result)
image_content_count = sum(isinstance(item, ImageContent) for item in result)
assert text_content_count == 2
assert image_content_count == 1
text_item = next(item for item in result if isinstance(item, TextContent))
assert text_item.text == '[\n {\n "a": 1\n },\n {\n "b": 2\n }\n]'
image_item = next(item for item in result if isinstance(item, ImageContent))
assert image_item.data == "ZmFrZWltYWdlZGF0YQ=="
def test_list_of_mixed_types_with_audio(self):
"""Test that a list of mixed types including Audio is converted correctly."""
content1 = TextContent(type="text", text="hello")
audio_obj = Audio(data=b"fakeaudiodata")
basic_data = {"a": 1}
result = _convert_to_content([content1, audio_obj, basic_data])
assert isinstance(result, list)
assert len(result) == 3
text_content_count = sum(isinstance(item, TextContent) for item in result)
audio_content_count = sum(isinstance(item, AudioContent) for item in result)
assert text_content_count == 2
assert audio_content_count == 1
text_item = next(item for item in result if isinstance(item, TextContent))
assert text_item.text == '{\n "a": 1\n}'
audio_item = next(item for item in result if isinstance(item, AudioContent))
assert audio_item.data == "ZmFrZWF1ZGlvZGF0YQ=="
def test_list_of_mixed_types_with_file(self):
"""Test that a list of mixed types including File is converted correctly."""
content1 = TextContent(type="text", text="hello")
file_obj = File(data=b"filedata", format="octet-stream")
basic_data = {"a": 1}
result = _convert_to_content([content1, file_obj, basic_data])
assert isinstance(result, list)
assert len(result) == 3
text_content_count = sum(isinstance(item, TextContent) for item in result)
embedded_content_count = sum(
isinstance(item, EmbeddedResource) and item.type == "resource"
for item in result
)
assert text_content_count == 2
assert embedded_content_count == 1
text_item = next(item for item in result if isinstance(item, TextContent))
assert text_item.text == '{\n "a": 1\n}'
embedded_item = next(
item
for item in result
if isinstance(item, EmbeddedResource) and item.type == "resource"
)
resource = embedded_item.resource
assert resource.mimeType == "application/octet-stream"
# Check for blob attribute and its value
assert hasattr(resource, "blob")
assert getattr(resource, "blob") == "ZmlsZWRhdGE="
def test_empty_list(self):
"""Test that an empty list results in an empty list."""
result = _convert_to_content([])
assert isinstance(result, list)
assert len(result) == 0
def test_empty_dict(self):
"""Test that an empty dictionary is converted to TextContent."""
result = _convert_to_content({})
assert isinstance(result, list)
assert len(result) == 1
assert isinstance(result[0], TextContent)
assert result[0].text == "{}"
def test_with_custom_serializer(self):
"""Test that a custom serializer is used for non-MCP types."""
def custom_serializer(data):
return f"Serialized: {data}"
result = _convert_to_content({"a": 1}, serializer=custom_serializer)
assert isinstance(result, list)
assert len(result) == 1
assert isinstance(result[0], TextContent)
assert result[0].text == "Serialized: {'a': 1}"
def test_custom_serializer_error_fallback(self, caplog):
"""Test that if a custom serializer fails, it falls back to the default."""
import logging
def custom_serializer_that_fails(data):
raise ValueError("Serialization failed")
with caplog.at_level(logging.WARNING):
result = _convert_to_content(
{"a": 1}, serializer=custom_serializer_that_fails
)
assert isinstance(result, list)
assert len(result) == 1
assert isinstance(result[0], TextContent)
# Should fall back to default serializer (pydantic_core.to_json)
assert result[0].text == '{\n "a": 1\n}'
assert "Error serializing tool result" in caplog.text
def test_process_as_single_item_flag(self):
"""Test that _process_as_single_item forces list to be treated as one item."""
result = _convert_to_content([1, "two", {"c": 3}], _process_as_single_item=True)
assert isinstance(result, list)
assert len(result) == 1
assert isinstance(result[0], TextContent)
assert result[0].text == '[\n 1,\n "two",\n {\n "c": 3\n }\n]'
content1 = TextContent(type="text", text="hello")
result = _convert_to_content([1, content1], _process_as_single_item=True)
assert isinstance(result, list)
assert len(result) == 1
assert isinstance(result[0], TextContent)
assert (
result[0].text
== '[\n 1,\n {\n "type": "text",\n "text": "hello",\n "annotations": null\n }\n]'
)