Unify MCP tool handlers around one result type

internal/agents/clients.go

@@ -35,9 +35,9 @@ func (m *Manager) clientShellTools() []mcp.Tool {
 				"The most recently active one is listed first. " +
 				"The human's iPhone is listed too, when byre's app is open on it; it takes only show_page, show_file and drive_page, and the other client tools fail there.",
 			InputSchema: json.RawMessage(`{"type": "object", "properties": {}}`),
-			Handler: func(ctx context.Context, raw json.RawMessage) (string, error) {
+			Handler: mcp.Typed(func(ctx context.Context, args struct{}) (string, error) {
 				return m.listClients(), nil
-			},
+			}),
 		},
 		{
 			Name: "client_bash",
@@ -134,7 +134,7 @@ func (m *Manager) clientTools(l *live) []mcp.Tool {
 				},
 				"required": ["client", "op"]
 			}`),
-			Rich: mcp.TypedRich(func(ctx context.Context, args drivePageArgs) mcp.Result {
+			Handler: mcp.TypedResult(func(ctx context.Context, args drivePageArgs) mcp.Result {
 				return m.drivePage(ctx, l, args)
 			}),
 		},
@@ -186,7 +186,7 @@ func (m *Manager) clientTools(l *live) []mcp.Tool {
 				},
 				"required": ["client", "path"]
 			}`),
-			Rich: mcp.TypedRich(m.clientRead),
+			Handler: mcp.TypedResult(m.clientRead),
 		},
 		{
 			Name:        "client_write",
@@ -264,7 +264,7 @@ func (m *Manager) clientTools(l *live) []mcp.Tool {
 				},
 				"required": ["client", "tool"]
 			}`),
-			Rich: mcp.TypedRich(m.clientHands),
+			Handler: mcp.TypedResult(m.clientHands),
 		},
 	}...)
 }

internal/agents/diagram.go

@@ -27,7 +27,7 @@ func (m *Manager) renderDiagramTool() mcp.Tool {
 			},
 			"required": ["source"]
 		}`),
-		Rich: mcp.TypedRich(func(ctx context.Context, args struct {
+		Handler: mcp.TypedResult(func(ctx context.Context, args struct {
 			Source string `json:"source"`
 		}) mcp.Result {
 			png, err := renderDiagram(ctx, args.Source)

internal/agents/files.go

@@ -38,7 +38,7 @@ func (m *Manager) fileTools(l *live) []mcp.Tool {
 				},
 				"required": ["path"]
 			}`),
-			Rich: mcp.TypedRich(func(ctx context.Context, args readArgs) mcp.Result {
+			Handler: mcp.TypedResult(func(ctx context.Context, args readArgs) mcp.Result {
 				return m.read(l, args)
 			}),
 		},

internal/agents/random.go

@@ -32,7 +32,7 @@ func (m *Manager) randomChoiceTool() mcp.Tool {
 			},
 			"required": ["choices"]
 		}`),
-		Rich: mcp.TypedRich(func(ctx context.Context, args struct {
+		Handler: mcp.TypedResult(func(ctx context.Context, args struct {
 			Choices []struct {
 				Choice string  `json:"choice"`
 				Weight float64 `json:"weight"`

internal/agents/ready.go

@@ -121,7 +121,7 @@ func (m *Manager) cancelReadyTool(l *live) mcp.Tool {
 		Description: "Withdraw your standing ready_for_merge or suggest_discard, when it no longer holds: for example the human raised a problem, or you found more work. " +
 			"The human then no longer sees the task as ready to merge or as suggested for discard; call ready_for_merge or suggest_discard again once it holds.",
 		InputSchema: json.RawMessage(`{"type": "object", "properties": {}}`),
-		Handler: func(ctx context.Context, raw json.RawMessage) (string, error) {
+		Handler: mcp.Typed(func(ctx context.Context, args struct{}) (string, error) {
 			err := m.store.ClearReady(ctx, l.taskID, agentActor, "")
 			if errors.Is(err, store.ErrNotFound) {
 				return "", fmt.Errorf("%w: this task has no standing ready_for_merge or suggest_discard", ErrConflict)
@@ -130,7 +130,7 @@ func (m *Manager) cancelReadyTool(l *live) mcp.Tool {
 				return "", err
 			}
 			return "Withdrawn: the human no longer sees this task as ready to merge or suggested for discard.", nil
-		},
+		}),
 	}
 }
 

internal/agents/snapshots.go

@@ -264,13 +264,13 @@ func (m *Manager) takeSnapshotTool(l *live) mcp.Tool {
 		Name:        "take_snapshot",
 		Description: takeSnapshotDescription + " It snapshots your own task's worktree.",
 		InputSchema: json.RawMessage(`{"type": "object", "properties": {}}`),
-		Handler: func(ctx context.Context, args json.RawMessage) (string, error) {
+		Handler: mcp.Typed(func(ctx context.Context, args struct{}) (string, error) {
 			err := m.RequestSnapshot(ctx, l.taskID)
 			if err != nil {
 				return "", err
 			}
 			return "Worktree committed to the task's branch, and snapshot requested. If the project has a review workflow, its reviewers check it against the default branch (a subtask's against its parent's branch); their findings come to you together once the workflow finishes.", nil
-		},
+		}),
 	}
 }
 

internal/mcp/server.go

@@ -13,35 +13,26 @@ type Tool struct {
 	Name        string
 	Description string
 	InputSchema json.RawMessage
-	Handler     func(ctx context.Context, args json.RawMessage) (string, error)
+	Handler     func(ctx context.Context, args json.RawMessage) Result
-	Rich        func(ctx context.Context, args json.RawMessage) Result
 }
 
-func decode[A any](raw json.RawMessage) (A, error) {
+func Typed[A any](run func(ctx context.Context, args A) (string, error)) func(ctx context.Context, raw json.RawMessage) Result {
-	args := *new(A)
+	return TypedResult(func(ctx context.Context, args A) Result {
-	err := json.Unmarshal(raw, &args)
+		text, err := run(ctx, args)
-	if err != nil {
-		return args, fmt.Errorf("malformed call: %w", err)
-	}
-	return args, nil
-}
-
-func Typed[A any](run func(ctx context.Context, args A) (string, error)) func(ctx context.Context, raw json.RawMessage) (string, error) {
-	return func(ctx context.Context, raw json.RawMessage) (string, error) {
-		args, err := decode[A](raw)
-		if err != nil {
-			return "", err
-		}
-		return run(ctx, args)
-	}
-}
-
-func TypedRich[A any](run func(ctx context.Context, args A) Result) func(ctx context.Context, raw json.RawMessage) Result {
-	return func(ctx context.Context, raw json.RawMessage) Result {
-		args, err := decode[A](raw)
 		if err != nil {
 			return TextResult(err.Error(), true)
 		}
+		return TextResult(text, false)
+	})
+}
+
+func TypedResult[A any](run func(ctx context.Context, args A) Result) func(ctx context.Context, raw json.RawMessage) Result {
+	return func(ctx context.Context, raw json.RawMessage) Result {
+		var args A
+		err := json.Unmarshal(raw, &args)
+		if err != nil {
+			return TextResult(fmt.Sprintf("malformed call: %s", err), true)
+		}
 		return run(ctx, args)
 	}
 }
@@ -120,7 +111,7 @@ func (t Tool) Call(ctx context.Context, args json.RawMessage) Result {
 	defer cancel()
 	done := make(chan Result, 1)
 	go func() {
-		done <- t.run(cctx, args)
+		done <- t.Handler(cctx, args)
 	}()
 	late := time.NewTimer(timeout + Grace)
 	defer late.Stop()
@@ -134,17 +125,6 @@ func (t Tool) Call(ctx context.Context, args json.RawMessage) Result {
 	}
 }
 
-func (t Tool) run(ctx context.Context, args json.RawMessage) Result {
-	if t.Rich != nil {
-		return t.Rich(ctx, args)
-	}
-	text, err := t.Handler(ctx, args)
-	if err != nil {
-		return TextResult(err.Error(), true)
-	}
-	return TextResult(text, false)
-}
-
 type Server struct {
 	Name    string
 	Version string