Imported from majiayu000/claude-skill-registry (skills/development/errors-confirmations-syedanabila559-phase2-3-todo-full-w-2/SKILL.md). Install upstream with npx skills add majiayu000/claude-skill-registry --skill errors-confirmations-syedanabila559-phase2-3-todo-full-w-2. Copyright stays with the author.

Errors & Confirmations Skill

This skill provides guidance for implementing graceful error handling and user confirmations.

Purpose

Implement graceful errors in backend/frontend:

• Tool not found → "Task not found, try again"
• Always confirm actions in response (e.g., "Task added!")
• Frontend: Show error toasts, loading indicators

When to Use

Use this skill when:

• Building error handling for chat API
• Creating user feedback mechanisms
• Implementing loading states
• Adding confirmation messages

Capabilities

• Backend Errors: Structured error responses with user-friendly messages
• Frontend Feedback: Toast notifications, loading states
• Action Confirmations: Clear success messages for user actions
• Error Recovery: Graceful degradation and retry suggestions

Backend Error Handling

Error Response Models

from pydantic import BaseModel
from typing import Optional, List
from enum import Enum

class ErrorSeverity(str, Enum):
    LOW = "low"
    MEDIUM = "medium"
    HIGH = "high"

class ErrorResponse(BaseModel):
    success: bool = False
    error: str
    message: str  # User-friendly message
    severity: ErrorSeverity = ErrorSeverity.MEDIUM
    retryable: bool = True
    suggestion: Optional[str] = None

class ToolError(Exception):
    def __init__(
        self,
        message: str,
        user_message: str,
        severity: ErrorSeverity = ErrorSeverity.MEDIUM,
        retryable: bool = True,
        suggestion: Optional[str] = None
    ):
        self.message = message
        self.user_message = user_message
        self.severity = severity
        self.retryable = retryable
        self.suggestion = suggestion
        super().__init__(message)

Error Handlers

from fastapi import Request, HTTPException
from fastapi.responses import JSONResponse

@app.exception_handler(ToolError)
async def tool_error_handler(request: Request, exc: ToolError):
    return JSONResponse(
        status_code=400 if exc.severity == ErrorSeverity.LOW else 500,
        content={
            "success": False,
            "error": exc.message,
            "message": exc.user_message,
            "severity": exc.severity.value,
            "retryable": exc.retryable,
            "suggestion": exc.suggestion
        }
    )

@app.exception_handler(HTTPException)
async def http_error_handler(request: Request, exc: HTTPException):
    user_messages = {
        400: "There was an issue with your request. Please check and try again.",
        401: "Please sign in to continue.",
        403: "You don't have permission for this action.",
        404: "The requested item was not found.",
        500: "Something went wrong on our end. Please try again."
    }

    return JSONResponse(
        status_code=exc.status_code,
        content={
            "success": False,
            "error": exc.detail,
            "message": user_messages.get(exc.status_code, "An error occurred"),
            "retryable": exc.status_code >= 500
        }
    )

Tool-Specific Errors

async def get_task_by_id(user_id: str, task_id: str) -> Task:
    """Get task with proper error handling."""
    result = await session.execute(
        select(Task).where(
            Task.id == task_id,
            Task.user_id == user_id
        )
    )
    task = result.scalar_one_or_none()

    if not task:
        raise ToolError(
            message=f"Task {task_id} not found",
            user_message="I couldn't find that task. It may have been deleted already.",
            severity=ErrorSeverity.LOW,
            retryable=False,
            suggestion="Try listing your tasks to see what's available."
        )

    return task

async def add_task(user_id: str, title: str, **kwargs) -> dict:
    """Add task with confirmation."""
    try:
        task = Task(user_id=user_id, title=title, **kwargs)
        session.add(task)
        await session.commit()
        await session.refresh(task)

        return {
            "success": True,
            "message": f"Task added successfully!",
            "task": task_to_dict(task)
        }

    except Exception as e:
        raise ToolError(
            message=f"Failed to add task: {str(e)}",
            user_message="I wasn't able to add that task. Please try again.",
            severity=ErrorSeverity.MEDIUM,
            retryable=True,
            suggestion="Check that the title isn't too long and try once more."
        )

Frontend Error Handling

Toast Notifications

// components/Toast.tsx
interface ToastProps {
  message: string;
  type: "success" | "error" | "info" | "warning";
  onClose: () => void;
}

export function Toast({ message, type, onClose }: ToastProps) {
  const styles = {
    success: "bg-green-500",
    error: "bg-red-500",
    info: "bg-blue-500",
    warning: "bg-yellow-500"
  };

  return (
    <div className={`toast ${styles[type]} fixed bottom-4 right-4 text-white px-4 py-3 rounded-lg shadow-lg flex items-center gap-2 animate-fade-in`}>
      <span>{type === "success" ? "✓" : type === "error" ? "✕" : "ℹ"}</span>
      <span>{message}</span>
      <button onClick={onClose} className="ml-2 hover:opacity-80">×</button>
    </div>
  );
}

Toast Container

// contexts/ToastContext.tsx
"use client";

import { createContext, useContext, useState, ReactNode } from "react";
import { Toast } from "@/components/Toast";

interface ToastItem {
  id: string;
  message: string;
  type: "success" | "error" | "info" | "warning";
}

interface ToastContextType {
  showToast: (message: string, type: ToastItem["type"]) => void;
}

const ToastContext = createContext<ToastContextType | null>(null);

export function ToastProvider({ children }: { children: ReactNode }) {
  const [toasts, setToasts] = useState<ToastItem[]>([]);

  const showToast = (message: string, type: ToastItem["type"]) => {
    const id = Date.now().toString();
    setToasts(prev => [...prev, { id, message, type }]);

    // Auto-remove after 5 seconds
    setTimeout(() => {
      setToasts(prev => prev.filter(t => t.id !== id));
    }, 5000);
  };

  return (
    <ToastContext.Provider value={{ showToast }}>
      {children}
      <div className="fixed bottom-4 right-4 z-50 space-y-2">
        {toasts.map(toast => (
          <Toast
            key={toast.id}
            message={toast.message}
            type={toast.type}
            onClose={() => setToasts(prev => prev.filter(t => t.id !== toast.id))}
          />
        ))}
      </div>
    </ToastContext.Provider>
  );
}

export function useToast() {
  const context = useContext(ToastContext);
  if (!context) {
    throw new Error("useToast must be used within ToastProvider");
  }
  return context;
}

Loading Indicator

// components/LoadingIndicator.tsx
export function LoadingIndicator() {
  return (
    <div className="flex items-center gap-2 text-gray-500 p-2">
      <div className="typing-dots">
        <span></span>
        <span></span>
        <span></span>
      </div>
      <span className="text-sm">Thinking...</span>
    </div>
  );
}

export function LoadingButton({
  children,
  loading,
  disabled,
  onClick,
  className = ""
}: {
  children: React.ReactNode;
  loading: boolean;
  disabled?: boolean;
  onClick?: () => void;
  className?: string;
}) {
  return (
    <button
      onClick={onClick}
      disabled={loading || disabled}
      className={`relative ${className}`}
    >
      {loading && (
        <span className="absolute inset-0 flex items-center justify-center">
          <Spinner />
        </span>
      )}
      <span className={loading ? "invisible" : ""}>{children}</span>
    </button>
  );
}

function Spinner() {
  return (
    <svg className="animate-spin h-5 w-5" viewBox="0 0 24 24">
      <circle
        className="opacity-25"
        cx="12"
        cy="12"
        r="10"
        stroke="currentColor"
        strokeWidth="4"
        fill="none"
      />
      <path
        className="opacity-75"
        fill="currentColor"
        d="M4 12a8 8 0 018-8V0C5.373 0 0 5.373 0 12h4zm2 5.291A7.962 7.962 0 014 12H0c0 3.042 1.135 5.824 3 7.938l3-2.647z"
      />
    </svg>
  );
}

Error Boundary

// components/ErrorBoundary.tsx
"use client";

import { Component, ReactNode } from "react";
import { useToast } from "@/contexts/ToastContext";

interface ErrorBoundaryProps {
  children: ReactNode;
  fallback?: ReactNode;
}

interface State {
  hasError: boolean;
  error?: Error;
}

export class ErrorBoundary extends Component<ErrorBoundaryProps, State> {
  state: State = { hasError: false };

  static getDerivedStateFromError(error: Error): State {
    return { hasError: true, error };
  }

  componentDidCatch(error: Error, errorInfo: any) {
    console.error("Error caught by boundary:", error, errorInfo);
  }

  render() {
    if (this.state.hasError) {
      if (this.props.fallback) {
        return this.props.fallback;
      }

      return (
        <div className="p-4 bg-red-50 border border-red-200 rounded-lg">
          <h3 className="font-bold text-red-800">Something went wrong</h3>
          <p className="text-red-600 mt-1">Please refresh the page and try again.</p>
          <button
            onClick={() => this.setState({ hasError: false })}
            className="mt-2 px-4 py-2 bg-red-600 text-white rounded hover:bg-red-700"
          >
            Try Again
          </button>
        </div>
      );
    }

    return this.props.children;
  }
}

Confirmation Messages

# Backend confirmation templates
CONFIRMATIONS = {
    "add_task": "✓ Task added! I've created '{title}' for you.",
    "complete_task": "✓ Done! '{title}' is marked as complete.",
    "delete_task": "✓ Removed '{title}' from your tasks.",
    "update_task": "✓ Updated '{title}' with your changes.",
    "list_tasks": "Here are your {count} {status} tasks:"
}

def format_confirmation(action: str, **kwargs) -> str:
    """Format a confirmation message."""
    template = CONFIRMATIONS.get(action, "✓ Action completed!")
    return template.format(**kwargs)

API Response Wrapper

def success_response(
    message: str,
    data: Optional[dict] = None,
    confirmation: bool = True
) -> dict:
    """Create a success response with optional confirmation."""
    response = {
        "success": True,
        "message": message,
        "confirmation": confirmation
    }
    if data:
        response["data"] = data
    return response

def error_response(
    user_message: str,
    error: Optional[str] = None,
    suggestion: Optional[str] = None
) -> dict:
    """Create an error response."""
    return {
        "success": False,
        "message": user_message,
        "error": error,
        "suggestion": suggestion
    }

Verification Checklist

• Tool errors return user-friendly messages
• Backend confirms actions ("Task added!")
• Frontend shows toast notifications
• Loading indicators during API calls
• Error boundary catches React errors
• Suggestions provided for recovery
• Graceful degradation on failures