error-handling-patterns

name	error-handling-patterns
description	Use when implementing error handling across the API, frontend, or MCP server

Error Handling Patterns

Flask API

from flask import abort

abort(404, description="Skill not found")
abort(403, description="Division not authorized")
abort(409, description="Already exists")
abort(422, description="Validation error")

React API Client

// apps/web/src/lib/api.ts
async function handleResponse(res: Response) {
  if (res.status === 401) { clearToken(); window.location.reload(); }
  if (res.status === 403) { throw new Error("Access denied"); }
  if (res.status === 404) { throw new Error("Not found"); }
  if (!res.ok) { throw new Error(await res.text()); }
  return res.json();
}

MCP Tool Errors

return {"success": False, "error": "division_restricted",
        "message": "Your division is not authorized for this skill"}

Error Response Schema

{"description": "Human-readable error message"}

For validation: {"messages": {"field": ["Error message"]}}

References

• Auth blueprint: apps/api/skillhub_flask/blueprints/auth.py
• API client: apps/web/src/lib/api.ts
• MCP tools: apps/mcp-server/skillhub_mcp/tools/