Integrate FastMCP

This commit integrates FastMCP, a high-level MCP server implementation originally written by Jeremiah Lowin,
into the official MCP SDK. It also updates dependencies and adds new dev dependencies.
It moves the existing SDK into a .lowlevel .

tests/server/fastmcp/resources/test_function_resources.py

@@ -0,0 +1,115 @@
+from pydantic import BaseModel, AnyUrl
+import pytest
+from mcp.server.fastmcp.resources import FunctionResource
+
+
+class TestFunctionResource:
+    """Test FunctionResource functionality."""
+
+    def test_function_resource_creation(self):
+        """Test creating a FunctionResource."""
+
+        def my_func() -> str:
+            return "test content"
+
+        resource = FunctionResource(
+            uri=AnyUrl("fn://test"),
+            name="test",
+            description="test function",
+            fn=my_func,
+        )
+        assert str(resource.uri) == "fn://test"
+        assert resource.name == "test"
+        assert resource.description == "test function"
+        assert resource.mime_type == "text/plain"  # default
+        assert resource.fn == my_func
+
+    async def test_read_text(self):
+        """Test reading text from a FunctionResource."""
+
+        def get_data() -> str:
+            return "Hello, world!"
+
+        resource = FunctionResource(
+            uri=AnyUrl("function://test"),
+            name="test",
+            fn=get_data,
+        )
+        content = await resource.read()
+        assert content == "Hello, world!"
+        assert resource.mime_type == "text/plain"
+
+    async def test_read_binary(self):
+        """Test reading binary data from a FunctionResource."""
+
+        def get_data() -> bytes:
+            return b"Hello, world!"
+
+        resource = FunctionResource(
+            uri=AnyUrl("function://test"),
+            name="test",
+            fn=get_data,
+        )
+        content = await resource.read()
+        assert content == b"Hello, world!"
+
+    async def test_json_conversion(self):
+        """Test automatic JSON conversion of non-string results."""
+
+        def get_data() -> dict:
+            return {"key": "value"}
+
+        resource = FunctionResource(
+            uri=AnyUrl("function://test"),
+            name="test",
+            fn=get_data,
+        )
+        content = await resource.read()
+        assert isinstance(content, str)
+        assert '"key": "value"' in content
+
+    async def test_error_handling(self):
+        """Test error handling in FunctionResource."""
+
+        def failing_func() -> str:
+            raise ValueError("Test error")
+
+        resource = FunctionResource(
+            uri=AnyUrl("function://test"),
+            name="test",
+            fn=failing_func,
+        )
+        with pytest.raises(ValueError, match="Error reading resource function://test"):
+            await resource.read()
+
+    async def test_basemodel_conversion(self):
+        """Test handling of BaseModel types."""
+
+        class MyModel(BaseModel):
+            name: str
+
+        resource = FunctionResource(
+            uri=AnyUrl("function://test"),
+            name="test",
+            fn=lambda: MyModel(name="test"),
+        )
+        content = await resource.read()
+        assert content == '{"name": "test"}'
+
+    async def test_custom_type_conversion(self):
+        """Test handling of custom types."""
+
+        class CustomData:
+            def __str__(self) -> str:
+                return "custom data"
+
+        def get_data() -> CustomData:
+            return CustomData()
+
+        resource = FunctionResource(
+            uri=AnyUrl("function://test"),
+            name="test",
+            fn=get_data,
+        )
+        content = await resource.read()
+        assert isinstance(content, str)