How to Avoid Common Mistakes When Integrating External Services

Introduction: The Hidden Pitfalls of External Service Integration

When you ask an AI coding agent to "Add Google login with Supabase Auth," it generates code in seconds. But when you run it, you see errors like supabase.auth.signIn is not a function. Why does this happen?

AI agents remember APIs from their training data cutoff, which means they may not know about the latest version changes. This is especially problematic with rapidly evolving services like Supabase, Firebase, and Stripe. They often suggest deprecated functions or incorrect configuration methods.

The bigger problem is that these integration mistakes are hard to debug. Network requests are sent but receive no response, authentication tokens are issued but sessions don't persist - symptoms are often ambiguous.

This article presents a systematic approach to safely integrating external services with AI, based on real Supabase Auth integration experience.

3-Step Preparation for Safe Integration

Before starting external service integration, following these three steps can significantly reduce mistakes.

Step 1: Activate Documentation Reference Tools

Enable Context-7 MCP so AI can reference the latest documentation. Context-7 is an MCP tool that provides web search and documentation reference capabilities, available in Claude Code and Cursor.

Give explicit instructions to AI:

"Before implementing Supabase Auth, use Context-7 to reference the latest authentication guide from the official Supabase documentation. Specifically check the latest API for the JavaScript client library."

This way, AI writes code based on real-time official documentation rather than training data.

Step 2: Analyze Entire Codebase

Before writing integration code, understand the current project structure and existing code. Use codebase analysis tools like Reformix.

"Call Reformix to analyze the current codebase. Specifically check if there's existing authentication-related code and what the API call patterns are."

During this process, verify:

• Existing authentication libraries or patterns in use
• How environment variables are configured
• Where API clients are initialized
• Error handling conventions

Step 3: Establish Implementation Plan

Don't write code immediately - first ask AI to explain the implementation plan.

"Explain the optimal implementation plan for applying Supabase Auth to this project step by step. For each step, specify which files to modify and what code to add."

While reviewing the plan, check:

• Whether environment variable setup is included
• If client initialization location is appropriate
• Whether auth state management aligns with existing patterns
• If error handling logic is included

Once the plan is sound, then begin implementation.

Real-World Case: Supabase Auth Integration Process

Let's walk through the step-by-step process of integrating Supabase Auth in an actual project.

Stage 1: Supabase Project Setup

Create a new project in the Supabase console and obtain:

• Project URL: https://xxxxx.supabase.co
• Anon Key: Public API key

Add to environment variables file (.env.local):

NEXT_PUBLIC_SUPABASE_URL=https://xxxxx.supabase.co
NEXT_PUBLIC_SUPABASE_ANON_KEY=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...

Stage 2: Enable Google OAuth Provider

Enable Google in Supabase console's Authentication > Providers. Create an OAuth client ID in Google Cloud Console and configure it.

Stage 3: Request AI Implementation

Now with everything prepared, request AI:

"Implement a Google login button with the Supabase project we just configured. When the button is clicked, show a Google login popup, and after successful login, save user information to the session."

AI generated this code:

// lib/supabase.ts
import { createClient } from '@supabase/supabase-js'

export const supabase = createClient(
  process.env.NEXT_PUBLIC_SUPABASE_URL!,
  process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY!
)

// components/LoginButton.tsx
'use client'

import { supabase } from '@/lib/supabase'

export function LoginButton() {
  const handleLogin = async () => {
    const { error } = await supabase.auth.signInWithOAuth({
      provider: 'google',
    })
    if (error) console.error('Login failed:', error)
  }

  return <button onClick={handleLogin}>Login with Google</button>
}

Stage 4: Verify Functionality

Clicking the login button opens the Google login popup, and after authentication, we confirmed the session was successfully created.

Check in browser developer tools Network tab:

• Is /auth/v1/authorize request being sent
• Is the response status 200
• Is the session token being returned

Solving RLS Issues and MVP Strategy

Supabase has Row Level Security (RLS) enabled by default. RLS is a powerful security feature that controls user-level access at the database level, but it increases complexity during the MVP stage.

Typical RLS Errors

Login succeeds, but when trying to query data, you see errors like:

Error: new row violates row-level security policy for table "users"

Or data queries only return empty arrays.

RLS Strategy for MVP Stage

In the actual project, we approached it this way:

1. First disable RLS completely to verify authentication flow works correctly
2. After completing core features, progressively add RLS policies table by table
3. Apply appropriate RLS policies to all tables before final deployment

How to disable RLS in Supabase console for each table:

-- Disable RLS per table
ALTER TABLE users DISABLE ROW LEVEL SECURITY;
ALTER TABLE posts DISABLE ROW LEVEL SECURITY;

When strengthening security later, add policies like:

-- Users can only view their own data
CREATE POLICY "Users can view own data"
ON users FOR SELECT
USING (auth.uid() = id);

-- Users can only update their own data
CREATE POLICY "Users can update own data"
ON users FOR UPDATE
USING (auth.uid() = id);

Verification Methods

Once integration is complete, check:

• In browser developer tools Network tab, verify API requests are being sent correctly
• In Application tab > Local Storage, verify Supabase session token is stored
• Test complete user flow from start to finish (login → data query → logout)

Systematizing External Service Integration with Vooster AI

External service integration, once tangled, takes more than double the debugging time. Vooster AI supports safe integration through MCP tools and project documentation.

1. Real-time Document Sync with 31 MCP Tools

Vooster AI's MCP synchronizes project state in real-time. When used with Context-7:

• AI writes code referencing latest official documentation
• Maintains consistency with tech stack specified in TRD (Technical Requirements Document)
• Implements with consistent patterns according to Code Guidelines

2. Specify External Services in TRD

When adding Supabase to the tech stack during project creation, AI automatically generates TRD. TRD includes:

• Supabase client version
• Authentication methods (OAuth, Magic Link, etc.)
• Database schema
• Environment variable configuration

With TRD, AI generates code in a consistent manner.

3. Add Integration Rules to Code Guidelines

Vooster AI auto-generates Code Guidelines per project. You can add external service integration rules here:

"When integrating external APIs, always verify latest official documentation with Context-7." "Initialize Supabase client as a single instance in lib/supabase.ts." "Wrap all auth errors in try-catch and display clear error messages to users."

AI will automatically follow these rules when writing code.

4. Validate by Task Units

Manage integration work in granular tasks on Vooster AI's task board:

• T-001: Supabase project setup and environment variable configuration
• T-002: Enable Google OAuth provider
• T-003: Implement login button UI
• T-004: Implement session management logic
• T-005: Set RLS policies (before deployment)

Validating each completed task means if issues arise, you can quickly resolve them with a narrowed scope.

Conclusion

The most important aspects of external service integration are referencing latest documentation and validating step by step. While AI coding tools are powerful, they remember APIs from their training time, so you must activate real-time documentation reference with tools like Context-7.

As seen in the Supabase Auth case, following this sequence greatly reduces integration mistakes:

1. Reference latest docs with Context-7 MCP
2. Analyze codebase with Reformix
3. Request implementation plan from AI first
4. Review plan then implement step by step
5. Verify API requests with Network tab
6. Defer complex features like RLS until later in MVP

Vooster AI systematically supports this entire process through 31 MCP tools, TRD, and Code Guidelines. External service integration, once tangled, takes double the time. Safely integrate by synchronizing documentation and code with Vooster AI's MCP.

Start your systematic vibe coding journey with Vooster AI today!