diff --git a/apps/backend/internal/mcp/server/handoff_handlers.go b/apps/backend/internal/mcp/server/handoff_handlers.go
index 3b12baf53b..528cade664 100644
--- a/apps/backend/internal/mcp/server/handoff_handlers.go
+++ b/apps/backend/internal/mcp/server/handoff_handlers.go
@@ -9,24 +9,31 @@ import (
 	"github.com/mark3labs/mcp-go/server"
 )
 
-// registerHandoffTools registers the office task-handoff MCP tools:
-// list_related_tasks_kandev, list_task_documents_kandev,
-// get_task_document_kandev, write_task_document_kandev. These are
-// available in ModeOffice and ModeTask so both office coordinators and
-// task assignees can read parent / sibling documents and write
-// child→parent coordination docs.
-func (s *Server) registerHandoffTools() {
+// registerRelatedTasksTool registers list_related_tasks_kandev, which lets an
+// agent discover parent / child / sibling / blocker task IDs. Useful in both
+// kanban (ModeTask) and office (ModeOffice) modes — kanban agents commonly use
+// it to find a sibling task to send a follow-up to via message_task_kandev.
+func (s *Server) registerRelatedTasksTool() {
 	s.mcpServer.AddTool(
 		mcp.NewTool("list_related_tasks_kandev",
 			mcp.WithDescription(
 				`List parent, children, siblings, blockers, and blocked tasks for the current task.
-Use this to discover task IDs you can read documents from. Document keys are included so you can pick
-the document to fetch with get_task_document_kandev. Pass task_id to inspect a different task in the same workspace.`,
+Use this to discover task IDs you can reach via message_task_kandev. In office mode, document keys are
+also included so you can fetch documents with get_task_document_kandev.
+Pass task_id to inspect a different task in the same workspace.`,
 			),
 			mcp.WithString("task_id", mcp.Description("Defaults to the current task.")),
 		),
 		s.wrapHandler("list_related_tasks_kandev", s.listRelatedTasksHandler()),
 	)
+}
+
+// registerTaskDocumentTools registers the cross-task document tools used for
+// office parent/child coordination: list_task_documents_kandev,
+// get_task_document_kandev, write_task_document_kandev. These are office-only
+// — kanban tasks don't use the document handoff pattern, so the surface is
+// kept lean.
+func (s *Server) registerTaskDocumentTools() {
 	s.mcpServer.AddTool(
 		mcp.NewTool("list_task_documents_kandev",
 			mcp.WithDescription(
diff --git a/apps/backend/internal/mcp/server/server.go b/apps/backend/internal/mcp/server/server.go
index 1db879659d..8fe3b8f1d2 100644
--- a/apps/backend/internal/mcp/server/server.go
+++ b/apps/backend/internal/mcp/server/server.go
@@ -314,7 +314,8 @@ func (s *Server) registerTools() {
 		// surface for office mode only keeps:
 		//   - ask_user_question — interactive prompt path
 		//   - plan tools        — structured plan capture
-		//   - handoff tools     — workflow handoff between steps
+		//   - related-tasks     — discover parent/child/sibling IDs
+		//   - task-document tools — parent/child coordination docs
 		// delegate_task was removed in favour of
 		// `agentctl kandev tasks create --parent $KANDEV_TASK_ID …`.
 		if !s.disableAskQuestion {
@@ -323,9 +324,14 @@ func (s *Server) registerTools() {
 		}
 		s.registerPlanTools()
 		count += 4
-		s.registerHandoffTools()
-		count += 4
+		s.registerRelatedTasksTool()
+		count++
+		s.registerTaskDocumentTools()
+		count += 3
 	default: // ModeTask
+		// Kanban tasks get list_related_tasks_kandev (useful for finding
+		// a sibling to message_task_kandev) but NOT the task-document
+		// tools — those are office coordination plumbing.
 		s.registerKanbanTools()
 		count += 11
 		if !s.disableAskQuestion {
@@ -334,8 +340,8 @@ func (s *Server) registerTools() {
 		}
 		s.registerPlanTools()
 		count += 4
-		s.registerHandoffTools()
-		count += 4
+		s.registerRelatedTasksTool()
+		count++
 	}
 	s.logger.Info("registered MCP tools",
 		zap.String("mode", s.mode),
diff --git a/apps/backend/internal/mcp/server/server_test.go b/apps/backend/internal/mcp/server/server_test.go
index 63f3d411b1..48ae27f493 100644
--- a/apps/backend/internal/mcp/server/server_test.go
+++ b/apps/backend/internal/mcp/server/server_test.go
@@ -59,6 +59,13 @@ func TestServerModeTask_RegistersCorrectTools(t *testing.T) {
 	assert.Contains(t, tools, "list_agents_kandev")
 	assert.Contains(t, tools, "list_executor_profiles_kandev")
 
+	// Task mode keeps list_related_tasks_kandev (sibling discovery) but
+	// drops the task-document tools — those are office-only.
+	assert.Contains(t, tools, "list_related_tasks_kandev")
+	assert.NotContains(t, tools, "list_task_documents_kandev")
+	assert.NotContains(t, tools, "get_task_document_kandev")
+	assert.NotContains(t, tools, "write_task_document_kandev")
+
 	// Task mode should NOT have config/mutation tools
 	assert.NotContains(t, tools, "create_workflow_kandev")
 	assert.NotContains(t, tools, "update_workflow_kandev")
@@ -197,8 +204,9 @@ func TestServerModeTask_ToolCount(t *testing.T) {
 
 	s := New(backend, "test-session", "test-task", 10005, log, "", false, ModeTask)
 	tools := getRegisteredToolNames(s)
-	// 11 kanban + 1 interaction + 4 plan + 4 handoff = 20
-	assert.Equal(t, 20, len(tools))
+	// 11 kanban + 1 interaction + 4 plan + 1 related-tasks = 17.
+	// Task-document tools (list/get/write) are office-only.
+	assert.Equal(t, 17, len(tools))
 }
 
 func TestServerModeConfig_ToolCount(t *testing.T) {
@@ -279,8 +287,8 @@ func TestServerModeOffice_ToolCount(t *testing.T) {
 
 	s := New(backend, "test-session", "test-task", 10005, log, "", false, ModeOffice)
 	tools := getRegisteredToolNames(s)
-	// 4 plan + 1 interaction + 4 handoff = 9 (delegate_task_kandev
-	// retired in favour of `agentctl kandev task create …`).
+	// 4 plan + 1 interaction + 1 related-tasks + 3 task-documents = 9
+	// (delegate_task_kandev retired in favour of `agentctl kandev task create …`).
 	assert.Equal(t, 9, len(tools))
 }
 
@@ -298,7 +306,7 @@ func TestServerModeOffice_DisableAskQuestion(t *testing.T) {
 	// delegate_task_kandev was retired from ModeOffice (now lives in
 	// the agentctl CLI as `agentctl kandev task create --parent …`).
 	assert.NotContains(t, tools, "delegate_task_kandev")
-	// 4 plan + 4 handoff = 8 (no ask_user_question, no delegate)
+	// 4 plan + 1 related-tasks + 3 task-documents = 8 (no ask_user_question, no delegate)
 	assert.Equal(t, 8, len(tools))
 }