Agent and tool flow

sequenceDiagram
  participant App as Application
  participant Agent as ChatAgent
  participant Model as ChatModel
  participant Tool as ChatTool
  App->>Agent: reply(conversation, user message)
  Agent->>Model: messages + tool definitions
  Model-->>Agent: assistant message + tool calls
  loop each tool round
      Agent->>Tool: execute(call, ToolRuntime)
      Tool-->>Agent: ToolExecutionResult
      Agent->>Model: tool-result messages
  end
  Agent-->>App: updated Conversation

The application configures ToolRuntime once and owns its context, store, and progress writer. Providers only translate the portable model protocol; they never invoke application tools.