flutter3d_mcp_kit

The parts every flutter3d MCP server shares, written once:

• OfferedTool<S, A> holds a tool and the code that runs it in one value, so every tool a server offers has a body.
• ToolTableServer<S, A> is a server built from a list of those over one session.
• Answer and PictureAnswer carry what a call did and the sentence to say about it. resultOf and pictureResultOf turn a refusal into an error result the agent reads, so the server itself does not fail.
• LoopbackMcpServer serves any of those servers over 127.0.0.1 HTTP with a per-server token, for an application that wants to hand an agent the session a person already has open.

flutter3d_editor_mcp, flutter3d_model_mcp and flutter3d_sim_mcp (with both of its servers) are built on it. It is plain Dart, so a server that uses it starts without the Flutter SDK.