MCP Client | Tasks

The tasks extension (io.modelcontextprotocol/tasks) of the MCP protocol version 2026-07-28 lets a server run a long tools/call in the background. Instead of the tool result, the server returns a task handle, and the client asks for the task status until the task finishes. The methods of this topic raise an exception in the legacy era.

 

Enabling tasks

Set MCPOptions.Tasks.Enabled to True. The client then declares the extension in _meta.clientCapabilities of every request, and the server decides for each tools/call whether it runs as a task.

Property	Description
Enabled	Declares the tasks extension. Default False.
AutoPoll	When True, a background thread polls tasks/get until the task reaches a terminal status. Default True.

 

Task lifecycle

• When a tools/call returns resultType task, OnMCPTaskCreated is raised first. Then OnMCPResponseTool is raised as usual, with the raw task handle JSON in aResponse.TaskResult.
• With AutoPoll the client calls tasks/get every pollIntervalMs milliseconds (1000 when the server sends none). OnMCPTaskStatus is raised every time the status, the status message or the requested inputs change.
• When the task reaches completed, failed or cancelled, OnMCPTaskCompleted is raised and polling stops. Read the tool result from aTask.Result or the error from aTask.Error.
• If the status is input_required, the inputs are answered like a Multi Round-Trip Request (legacy handlers first, then OnMCPInputRequired with aMethod tasks/update) and sent with tasks/update.
• If the server no longer knows the task, it is reported as failed. If the task time to live passes, the error is reported through OnError and polling stops.

 

Manual control

• TasksGet: requests the status of a task, raises OnMCPTaskStatus and returns the status.
• TasksUpdate: sends the answers of the inputs requested by a task.
• TasksCancel: asks the server to cancel a task and stops its poller.

 

TsgcAI_MCP_Client_Task

Property	Description
TaskId	Id of the task assigned by the server.
ToolName	Name of the tool that created the task.
Status	aimcptskWorking, aimcptskInputRequired, aimcptskCompleted, aimcptskFailed or aimcptskCancelled.
StatusMessage	Optional message sent by the server with the status.
CreatedAt, LastUpdatedAt	ISO 8601 timestamps sent by the server.
TTLMs	Time to live in milliseconds, -1 when unlimited.
PollIntervalMs	Poll interval suggested by the server.
Result	Tool result as raw JSON when the task is completed.
Error	Error as raw JSON when the task failed.
InputRequests	Inputs requested by the server as raw JSON.
Text	Raw JSON of the last task message.
IsTerminal	True when the status is completed, failed or cancelled.

 

Threads

The events raised by the poller (OnMCPTaskStatus and OnMCPTaskCompleted) run in the background thread of the task. Use TThread.Queue or TThread.Synchronize to update visual controls. Pollers are stopped when Initialize is called again and when the component is destroyed.

The server side is described in MCP Server | Tasks.

Sample code

procedure TForm1.RunLongJob;
begin
  MCP.MCPOptions.Tasks.Enabled := True;
  MCP.MCPOptions.Tasks.AutoPoll := True;
  MCP.OnMCPTaskCreated := MCPTaskCreated;
  MCP.OnMCPTaskStatus := MCPTaskStatus;
  MCP.OnMCPTaskCompleted := MCPTaskCompleted;
  MCP.RequestTool('long_job');
end;

procedure TForm1.MCPTaskCreated(Sender: TObject;
  const aTask: TsgcAI_MCP_Client_Task);
begin
  FTaskId := aTask.TaskId;
end;

procedure TForm1.MCPTaskStatus(Sender: TObject;
  const aTask: TsgcAI_MCP_Client_Task);
begin
  Log(aTask.TaskId + ': ' + aTask.StatusMessage);
end;

procedure TForm1.MCPTaskCompleted(Sender: TObject;
  const aTask: TsgcAI_MCP_Client_Task);
begin
  if aTask.Status = aimcptskCompleted then
    Log('result: ' + aTask.Result)
  else
    Log('finished without result: ' + aTask.Error);
end;

procedure TForm1.CancelJob;
begin
  MCP.TasksCancel(FTaskId);
end;