Add ToolAnnotations support in FastMCP and lowlevel servers (#482)

tests/server/fastmcp/test_tool_manager.py

@@ -9,6 +9,7 @@ from mcp.server.fastmcp.exceptions import ToolError
 from mcp.server.fastmcp.tools import ToolManager
 from mcp.server.session import ServerSessionT
 from mcp.shared.context import LifespanContextT
+from mcp.types import ToolAnnotations
 
 
 class TestAddTools:
@@ -321,3 +322,43 @@ class TestContextHandling:
         ctx = mcp.get_context()
         with pytest.raises(ToolError, match="Error executing tool tool_with_context"):
             await manager.call_tool("tool_with_context", {"x": 42}, context=ctx)
+
+
+class TestToolAnnotations:
+    def test_tool_annotations(self):
+        """Test that tool annotations are correctly added to tools."""
+
+        def read_data(path: str) -> str:
+            """Read data from a file."""
+            return f"Data from {path}"
+
+        annotations = ToolAnnotations(
+            title="File Reader",
+            readOnlyHint=True,
+            openWorldHint=False,
+        )
+
+        manager = ToolManager()
+        tool = manager.add_tool(read_data, annotations=annotations)
+
+        assert tool.annotations is not None
+        assert tool.annotations.title == "File Reader"
+        assert tool.annotations.readOnlyHint is True
+        assert tool.annotations.openWorldHint is False
+
+    @pytest.mark.anyio
+    async def test_tool_annotations_in_fastmcp(self):
+        """Test that tool annotations are included in MCPTool conversion."""
+
+        app = FastMCP()
+
+        @app.tool(annotations=ToolAnnotations(title="Echo Tool", readOnlyHint=True))
+        def echo(message: str) -> str:
+            """Echo a message back."""
+            return message
+
+        tools = await app.list_tools()
+        assert len(tools) == 1
+        assert tools[0].annotations is not None
+        assert tools[0].annotations.title == "Echo Tool"
+        assert tools[0].annotations.readOnlyHint is True