chore: import upstream snapshot with attribution

examples/stories/error_handling/server.py

@@ -0,0 +1,35 @@
+"""Two error channels: ToolError -> is_error result; MCPError -> JSON-RPC protocol error."""
+
+from mcp_types import INVALID_PARAMS
+
+from mcp.server.mcpserver import MCPServer
+from mcp.server.mcpserver.exceptions import ToolError
+from mcp.shared.exceptions import MCPError
+from stories._hosting import run_server_from_args
+
+
+def build_server() -> MCPServer:
+    mcp = MCPServer("error-handling-example")
+
+    @mcp.tool()
+    def divide(a: float, b: float) -> float:
+        """Divide a by b. Division by zero is an execution error the LLM should see."""
+        if b == 0:
+            # ToolError is caught by the tool wrapper and returned as
+            # CallToolResult(is_error=True) — the LLM reads the message and can
+            # self-correct.
+            raise ToolError("cannot divide by zero")
+        return a / b
+
+    @mcp.tool()
+    def restricted() -> str:
+        """A tool that always rejects the caller at the protocol level."""
+        # MCPError escapes the tool wrapper and becomes a JSON-RPC error
+        # response — the *host* sees code/message/data, not the LLM.
+        raise MCPError(code=INVALID_PARAMS, message="this tool is gated", data={"reason": "demo"})
+
+    return mcp
+
+
+if __name__ == "__main__":
+    run_server_from_args(build_server)