How to Build a Real-Time Visa Appointment Checker: Complete MCP Protocol Development Guide
In our interconnected world, visa applications have become an unavoidable part of life for millions of people. Yet the tedious process of constantly refreshing visa appointment websites and manually checking for available slots frustrates countless applicants. This comprehensive guide will walk you through building an efficient visa appointment monitoring system using modern technology stack, helping developers quickly implement automated visa appointment tracking functionality.
What Is a Visa Appointment Checker System?
A visa appointment checker system is an automated tool that monitors visa center appointment slot availability in real-time. The system retrieves the latest appointment data through API interfaces and provides intelligent filtering and notification features, enabling users to secure appointment opportunities the moment they become available.
Traditional manual checking methods are not only inefficient but also prone to missing fleeting appointment slots. A modern monitoring system based on MCP (Model Context Protocol) can provide 24/7 continuous monitoring services, significantly improving appointment success rates.
Understanding MCP Protocol for Visa Checking
What Is the MCP Protocol?
MCP (Model Context Protocol) is an open standard protocol specifically designed to connect AI models with various data sources and tools. In visa appointment checking scenarios, the MCP protocol enables:
-
Standardized data exchange formats -
Efficient real-time communication mechanisms -
Flexible tool integration capabilities -
Scalable service architecture
Why Choose MCP Protocol?
Compared to traditional REST APIs or other communication protocols, MCP protocol offers significant advantages in visa checking applications:
Real-time Performance: Supports Server-Sent Events (SSE) for instant appointment status change notifications, ensuring users receive the latest information immediately.
Standardization Benefits: Unified protocol specifications reduce development complexity and improve system maintainability.
Intelligence Integration: Native support for AI model integration enables smart appointment reminders and personalized recommendation features.
Technical Architecture Deep Dive
Core Technology Stack Selection
This system employs a modern technology stack where each component has been carefully selected:
Bun Runtime: As a next-generation JavaScript runtime, Bun significantly outperforms Node.js with 7.5x faster installation speeds and 10x faster cold start times.
TypeScript Programming Language: Provides complete type safety guarantees, combined with Zod for runtime type validation, ensuring data processing reliability.
Hono Web Framework: Lightweight framework with only 14KB footprint, reducing resource usage by 93% compared to Express.
Vitest Testing Framework: Fast unit testing tool ensuring code quality and system stability.
System Architecture Design
Visa Checking System Architecture
├── Data Acquisition Layer
│ ├── visasbot.com API Integration
│ ├── Smart Caching Mechanism (5-minute cache)
│ └── Error Recovery and Fallback Strategy
├── Business Logic Layer
│ ├── Data Processing and Formatting
│ ├── Multi-dimensional Filtering
│ └── Status Monitoring and Alerts
├── Communication Protocol Layer
│ ├── stdio Transport (Local Communication)
│ ├── HTTP + SSE Transport (Remote Communication)
│ └── JSON-RPC Message Processing
└── User Interface Layer
├── Tool Interfaces
├── Resource Interfaces
└── Error Handling and Logging
Getting Started: Building from Scratch
Environment Setup
First, ensure your development environment has the Bun runtime installed. Installing Bun is straightforward:
# Install Bun (single command installation)
curl -fsSL https://bun.sh/install | bash
Project Initialization
Create the project directory and install dependencies:
# Create project directory
mkdir visa-checker-mcp
cd visa-checker-mcp
# Install dependencies using Bun (20-30x faster than npm)
bun install
Starting the Development Server
The system supports two operation modes for different use cases:
# stdio transport mode (suitable for local development and CLI tools)
bun run dev:stdio
# HTTP server mode (suitable for web applications and remote services)
bun run dev:http
Core Features Detailed
Real-time Visa Appointment Querying
The system’s core functionality is real-time querying of visa appointment slots. By integrating with the visasbot.com API interface, it can retrieve the latest appointment information from visa centers worldwide.
Data Retrieval Process:
-
System periodically sends requests to the API -
Retrieves structured appointment data -
Performs data cleaning and formatting -
Updates local cache information -
Pushes change notifications to users
Smart Caching Mechanism:
To avoid overwhelming the API server with frequent requests, the system implements a 5-minute intelligent caching strategy. When the API service is unavailable, the system automatically falls back to cached data, ensuring service continuity.
Multi-dimensional Filtering Capabilities
The system provides comprehensive filtering options, allowing users to perform precise queries based on specific needs:
Country Code Filtering: Support filtering by applicant’s country of origin, such as Turkey (tur), China (chn), etc.
Target Country Filtering: Specify the destination country for visa applications, such as Netherlands (nld), Germany (deu), etc.
Visa Type Filtering: Distinguish between tourist visas, business visas, student visas, and other types.
Appointment Status Filtering: Quickly filter visa centers with available appointment slots.
Three Core Tools
The system provides three main query tools, each designed for specific use cases:
1. fetch-visa-appointments Tool
This is the fundamental query tool that retrieves complete visa appointment data:
// Get all appointment information
await tool.call('fetch-visa-appointments', {})
// Filter by country (Turkey to Netherlands visa)
await tool.call('fetch-visa-appointments', {
country_code: 'tur',
mission_code: 'nld'
})
// Filter by status
await tool.call('fetch-visa-appointments', {
status: 'open'
})
2. get-open-appointments Tool
Specifically designed for querying visa centers with available appointment slots:
// Get all open appointments
await tool.call('get-open-appointments', {})
// Filter open appointments by country
await tool.call('get-open-appointments', {
country_code: 'tur'
})
3. search-visa-centers Tool
Provides the most powerful advanced search functionality:
await tool.call('search-visa-centers', {
country_code: 'tur',
mission_code: 'nld',
visa_type: 'tourism',
status: 'open'
})
System Integration and Deployment
Claude Desktop Integration
For users wanting to use this system within Claude Desktop, appropriate configuration is required:
{
"mcpServers": {
"visa-checker-mcp": {
"command": "/Users/username/.bun/bin/bun",
"args": ["/Users/username/Dev/visa-checker-mcp/src/index.ts"]
}
}
}
Path Configuration Tips:
Get the correct Bun path:
which bun
# Example output: /Users/username/.bun/bin/bun
Get project path:
echo "$(pwd)/src/index.ts"
# Example output: /Users/username/Dev/visa-checker-mcp/src/index.ts
Transport Protocol Selection
The system supports two transport protocols, adapting to different deployment scenarios:
stdio Transport Protocol:
-
Suitable for local development and CLI tools -
Direct inter-process communication -
Low latency, simple debugging -
Perfect match for Claude Desktop usage scenarios
HTTP + SSE Transport Protocol:
-
Suitable for web applications and remote services -
RESTful API endpoints -
Server-Sent Events support for real-time updates -
CORS cross-domain support -
Session management functionality
Performance Optimization and Monitoring
Performance Comparison Data
The system demonstrates significant advantages over traditional technology stacks:
Error Handling and Fallback Strategy
The system implements comprehensive error handling mechanisms:
API Timeout Protection: 10-second timeout limit prevents long waiting periods.
Automatic Fallback Mechanism: When API is unavailable, automatically uses cached data with warnings.
Transport-aware Logging: Automatically uses stderr for log output in stdio mode, avoiding interference with JSON-RPC communication.
Type Safety Validation: Uses Zod for runtime type checking, ensuring correct data formats.
Development Workflow and Testing
Development Environment Configuration
# Code quality checks
bun run lint
bun run format
# Type checking
bun run typecheck
# Unit testing
bun run test
# Build production version
bun run build
Testing Strategy
The system employs multi-layered testing strategies to ensure code quality:
Unit Testing: Uses Vitest framework to test core business logic.
Integration Testing: Verifies API integration and data processing workflows.
End-to-end Testing: Simulates real user scenarios for complete workflow verification.
Resource Management and Caching
Intelligent Resource Management
The system provides two main resource endpoints for accessing appointment data:
Complete Dataset Resource: visa://appointments – Returns comprehensive live visa appointment data in JSON format.
Filtered Dataset Resource: visa://appointments/{country_code}/{mission_code} – Returns filtered data by specific country codes and mission codes.
Caching Strategy Details
The 5-minute intelligent caching mechanism works as follows:
-
Initial Request: First API call retrieves fresh data and stores it in memory cache -
Subsequent Requests: Within 5 minutes, serve data from cache to reduce API load -
Cache Expiration: After 5 minutes, next request triggers fresh API call -
Fallback Protection: If API fails, serve cached data with appropriate warnings -
Error Recovery: System attempts API recovery while maintaining service availability
This approach balances real-time data accuracy with system performance and API rate limiting considerations.
Advanced Configuration Options
Custom Filtering Parameters
The system supports extensive filtering through various parameters:
Geographic Filtering:
-
country_code: Filter by applicant’s country (ISO 3-letter codes) -
mission_code: Filter by destination country/embassy (ISO 3-letter codes)
Service Type Filtering:
-
visa_type: Specify visa categories (tourism, business, study, family, etc.) -
service_type: Differentiate between regular and premium services
Availability Filtering:
-
status: Filter by appointment availability (open, closed, limited) -
date_range: Specify preferred appointment date ranges
Logging and Monitoring
The system implements sophisticated logging mechanisms:
Transport-aware Logging: Automatically detects communication mode (stdio vs HTTP) and routes log output appropriately to prevent interference with data transmission.
Structured Logging: All log entries include timestamps, severity levels, and contextual information for effective debugging.
Error Tracking: Comprehensive error logging with stack traces and recovery actions.
Production Deployment Considerations
Security Best Practices
When deploying to production environments, consider these security measures:
API Key Management: Store API keys securely using environment variables or secure key management services.
Rate Limiting: Implement client-side rate limiting to respect API service limits and prevent abuse.
Input Validation: Use Zod schemas for comprehensive input validation and sanitization.
Error Sanitization: Ensure error messages don’t expose sensitive system information.
Scalability Planning
For high-traffic scenarios, the system can be enhanced with:
Load Balancing: Deploy multiple instances behind a load balancer for increased capacity.
Database Integration: Replace in-memory caching with persistent storage solutions like Redis or databases.
Queue Systems: Implement job queues for handling large volumes of appointment checking requests.
Microservices Architecture: Split functionality into specialized microservices for better scalability.
Troubleshooting Common Issues
JSON Parsing Errors in MCP Server
This error typically occurs when using stdio transport due to console.log() output interfering with JSON-RPC messages. The solution is to use the system’s built-in transport-aware logging functionality, which automatically uses stderr output in stdio mode.
Error Symptoms:
-
Unexpected token '🔧', "🔧 Registe"... is not valid JSON -
Communication failures between client and server
Resolution Steps:
-
Replace all console.log() calls with the logger utility -
Ensure logging uses stderr in stdio mode -
Verify JSON-RPC messages use stdout exclusively
Claude Desktop Configuration Issues
Configuration problems often stem from incorrect path specifications or permission issues:
Common Problems and Solutions:
-
Use Absolute Paths: Relative paths won’t work in Claude Desktop configuration -
Verify Bun Path: Run which bunto get the correct command path -
Check File Permissions: Ensure TypeScript files are readable and executable -
Restart Claude Desktop: Configuration changes require application restart
Server Connection Problems
Follow these diagnostic steps for connection issues:
-
Local Testing: Run bun run dev:stdioto verify server starts correctly -
Check Logs: Review Claude Desktop logs for specific error messages -
Process Verification: Confirm server process starts and maintains connection -
Path Validation: Verify Bun is accessible at specified path
Path Configuration Verification
Test your configuration with these commands:
# Test Bun command availability
/path/to/bun --version
# Test server startup
/path/to/bun /path/to/your/project/src/index.ts
Project Extension and Customization
Adding New Visa Center Support
The system’s modular design makes adding new visa centers straightforward:
-
Service Layer Extension: Add new API adapters in the services directory -
Data Model Updates: Extend data models and validation rules -
Filter Enhancement: Expand filtering conditions and query parameters -
Test Coverage: Add comprehensive unit tests for new functionality
Custom Notification Integration
The system can easily integrate various notification methods:
Email Notifications: SMTP integration for appointment alerts
SMS Alerts: Mobile messaging service integration
Push Notifications: Web push or mobile app notifications
Chat Platform Integration: Slack, Discord, or Microsoft Teams notifications
Webhook Support: Custom webhook endpoints for third-party integrations
Data Persistence Extensions
While the system defaults to in-memory caching, it can be extended to support:
Redis Caching: Distributed caching for multi-instance deployments
Database Storage: Persistent storage with PostgreSQL, MySQL, or MongoDB
File System Caching: Local file-based caching for single-instance deployments
Cloud Storage Services: Integration with AWS S3, Google Cloud Storage, or Azure Blob Storage
Performance Tuning and Optimization
Memory Management
The system implements efficient memory usage patterns:
Cache Size Limits: Configurable memory limits prevent excessive resource consumption
Garbage Collection: Proper object cleanup and reference management
Memory Leak Prevention: Regular monitoring and cleanup of unused resources
API Optimization
Several strategies optimize API usage:
Request Batching: Combine multiple queries into single API calls when possible
Conditional Requests: Use HTTP conditional headers to minimize data transfer
Compression: Enable gzip compression for API responses
Connection Pooling: Maintain persistent connections to reduce overhead
Network Resilience
The system includes robust network handling:
Retry Logic: Automatic retry with exponential backoff for failed requests
Circuit Breaker: Prevent cascade failures during API outages
Health Checks: Regular API endpoint health monitoring
Graceful Degradation: Maintain partial functionality during service disruptions
Understanding the Visa Appointment Ecosystem
How Visa Appointment Systems Work
Modern visa appointment systems typically operate on a centralized booking platform that manages appointment slots across multiple visa centers. Understanding this ecosystem helps in building more effective monitoring tools:
Appointment Release Patterns: Most visa centers release appointments in batches at specific times, often early morning or late evening in local time zones.
Slot Duration: Appointment slots typically range from 15-30 minutes, with specific time blocks allocated for different visa types.
Cancellation Windows: Last-minute cancellations can create sudden availability, making real-time monitoring crucial.
Data Sources and APIs
The system primarily integrates with visasbot.com API, which aggregates appointment data from various official visa center websites:
Data Freshness: API data is typically updated every 5-15 minutes from source systems
Coverage: Supports major visa centers across Europe, North America, and Asia
Reliability: Provides fallback mechanisms when official websites are temporarily unavailable
Code Quality and Maintenance
Type Safety Implementation
The system leverages TypeScript’s type system extensively:
Interface Definitions: Clear contracts between system components
Generic Types: Reusable type definitions for different data structures
Runtime Validation: Zod schemas ensure data integrity at runtime
Type Guards: Custom type checking functions for complex data validation
Code Organization Principles
The project follows established patterns for maintainability:
Single Responsibility: Each module handles one specific concern
Dependency Injection: Loose coupling between components
Configuration Management: Centralized configuration with environment-specific overrides
Error Boundaries: Isolated error handling prevents cascade failures
Future Development Roadmap
Planned Enhancements
The system architecture supports several planned improvements:
Machine Learning Integration: Predictive analytics for appointment availability patterns
Multi-language Support: Internationalization for global user base
Mobile Applications: Native mobile apps for iOS and Android
Browser Extensions: Chrome and Firefox extensions for automated checking
Community Contributions
The open-source nature of the project encourages community involvement:
Feature Requests: User-driven feature prioritization
Bug Reports: Community-driven quality assurance
Documentation: Collaborative documentation improvements
Code Reviews: Peer review process for contributions
Conclusion
Building a visa appointment checker system using modern technologies like MCP protocol, Bun runtime, and TypeScript provides significant advantages over traditional approaches. The system we’ve explored offers real-time monitoring, intelligent filtering, automatic fallback mechanisms, and comprehensive error handling while maintaining high performance and reliability.
For individuals who frequently apply for visas or organizations providing visa services to clients, such automated systems can dramatically improve efficiency and reduce manual effort. The standardized design based on MCP protocol also provides an excellent foundation for future feature extensions and system integrations.
As global visa policies continue to evolve and digitization increases, automated tools like this will become increasingly important. Mastering these modern development technologies and architectural concepts not only solves current practical problems but also prepares developers for future technological developments.
Whether you’re a beginner or an experienced developer, this project provides an excellent learning and practice platform. From it, you can learn modern JavaScript runtime usage, TypeScript type-safe design, practical MCP protocol applications, and how to build a complete production-grade system.
The combination of performance optimization, robust error handling, comprehensive testing, and thoughtful architecture makes this visa appointment checker system a solid foundation for real-world deployment. The detailed troubleshooting guide and extension possibilities ensure that the system can adapt to various requirements and scale as needed.
By following the principles and practices outlined in this guide, developers can create reliable, efficient, and user-friendly systems that solve real problems while maintaining high code quality and professional standards.