API Request Validator Service

API Request Validator Service

Executive Summary

Background & Motivation

Problem Statement

• Malformed Requests: Invalid payloads causing API failures and wasted resources
• Security Vulnerabilities: Unvalidated input leading to injection attacks and data breaches
• Performance Issues: Oversized requests causing timeouts and resource exhaustion
• Cost Overruns: Invalid parameters leading to unnecessary API charges
• Provider Inconsistencies: Different validation requirements across AI providers
• Error Cascades: Invalid requests propagating through the system causing widespread failures

Why This Solution

• Early Validation: Catch errors before expensive API calls
• Security First: Comprehensive input sanitization and threat detection
• Provider Agnostic: Unified validation interface for all AI providers
• Performance Optimization: Request optimization and caching strategies
• Developer Experience: Clear error messages and validation feedback
• Compliance: Ensure requests meet regulatory and provider requirements

Goals & Non-Goals

Goals

1. Comprehensive Validation: Schema, syntax, and semantic validation of API requests
2. Security Hardening: Input sanitization, injection prevention, and threat detection
3. Performance Optimization: Request size limits, compression, and optimization
4. Provider Compatibility: Support for multiple AI provider validation requirements
5. Error Clarity: Detailed, actionable error messages for developers
6. Rate Limiting: Request throttling and quota management
7. Compliance: Validation for data protection and regulatory requirements

Non-Goals

1. Request Execution: Only validates, does not execute API requests
2. Response Validation: Focuses on outbound requests, not response validation
3. Business Logic: Pure technical validation, no domain-specific logic
4. Authentication: Validation only, credential management handled elsewhere

Technical Design

High-Level Architecture

Core Components

1. Schema Validator

• JSON Schema validation against provider specifications
• Type checking and format validation
• Required field validation
• Custom validation rules for AI-specific parameters

2. Security Validator

• Input sanitization and encoding validation
• SQL injection and XSS prevention
• Malicious payload detection
• Content filtering and safety checks

3. Performance Validator

• Payload size limits and compression
• Rate limiting and quota enforcement
• Request deduplication
• Performance optimization suggestions

4. Provider Validator

• Provider-specific parameter validation
• Model capability checking
• API version compatibility
• Custom validation logic per provider

5. Error Reporter

• Structured error reporting
• Validation path tracking
• Suggestion generation
• Localized error messages

API Specifications

Primary Interfaces

interface ValidationConfig {
  schemas: Record<string, SchemaDefinition>;
  security: SecurityConfig;
  performance: PerformanceConfig;
  providers: Record<string, ProviderValidationConfig>;
}

interface SchemaDefinition {
  jsonSchema: JSONSchema7;
  customValidators?: CustomValidator[];
  strictMode?: boolean;
}

interface SecurityConfig {
  sanitization: {
    enabled: boolean;
    allowedTags?: string[];
    stripTags?: boolean;
  };
  injectionPrevention: {
    sqlInjection: boolean;
    xssProtection: boolean;
    commandInjection: boolean;
  };
  contentFiltering: {
    enabled: boolean;
    blockedPatterns?: RegExp[];
    maxContentLength?: number;
  };
}

interface PerformanceConfig {
  limits: {
    maxPayloadSize: number; // bytes
    maxRequestsPerMinute: number;
    maxRequestsPerHour: number;
  };
  optimization: {
    compressionEnabled: boolean;
    deduplicationEnabled: boolean;
    cachingEnabled: boolean;
  };
}

interface ProviderValidationConfig {
  name: string;
  modelLimits: Record<string, ModelLimits>;
  customRules: ValidationRule[];
  apiVersion: string;
}

interface ModelLimits {
  maxTokens: number;
  supportedFormats: string[];
  maxImages?: number;
  maxFileSize?: number;
}

interface ValidationRequest {
  provider: string;
  endpoint: string;
  method: string;
  headers?: Record<string, string>;
  body?: any;
  metadata?: {
    userId?: string;
    sessionId?: string;
    priority?: 'low' | 'normal' | 'high';
  };
}

interface ValidationResult {
  isValid: boolean;
  errors: ValidationError[];
  warnings: ValidationWarning[];
  suggestions?: OptimizationSuggestion[];
  metadata: {
    validationTime: number;
    rulesApplied: string[];
    provider: string;
    requestId: string;
  };
}

interface ValidationError {
  code: string;
  message: string;
  path: string;
  severity: 'error' | 'critical';
  details?: any;
  suggestions?: string[];
}

interface ValidationWarning {
  code: string;
  message: string;
  path: string;
  impact: 'performance' | 'cost' | 'compatibility';
  suggestion?: string;
}

interface OptimizationSuggestion {
  type: 'compression' | 'parameter_optimization' | 'model_selection';
  description: string;
  potentialSavings?: {
    cost?: number;
    time?: number;
    tokens?: number;
  };
}

// Main service interface
interface ApiRequestValidator {
  // Core validation
  validateRequest(request: ValidationRequest): Promise<ValidationResult>;
  validateBatch(requests: ValidationRequest[]): Promise<ValidationResult[]>;
  
  // Schema management
  registerSchema(provider: string, schema: SchemaDefinition): Promise<void>;
  updateSchema(provider: string, schema: SchemaDefinition): Promise<void>;
  getSchema(provider: string): Promise<SchemaDefinition | null>;
  
  // Rule management
  addCustomRule(provider: string, rule: ValidationRule): Promise<void>;
  removeCustomRule(provider: string, ruleId: string): Promise<void>;
  listRules(provider?: string): Promise<ValidationRule[]>;
  
  // Performance and metrics
  getValidationStats(timeRange?: TimeRange): Promise<ValidationStats>;
  clearCache(): Promise<void>;
  
  // Configuration
  updateConfig(config: Partial<ValidationConfig>): Promise<void>;
  getConfig(): Promise<ValidationConfig>;
}

Integration with API Connector Service

// API Connector Service integration
class ApiConnectorService {
  constructor(
    private config: ApiConnectorConfig,
    private requestValidator: ApiRequestValidator
  ) {}

  async makeRequest<T>(request: ApiRequest): Promise<ApiResponse<T>> {
    // Convert to validation request format
    const validationRequest: ValidationRequest = {
      provider: request.provider || 'auto',
      endpoint: request.endpoint,
      method: request.method,
      headers: request.headers,
      body: request.body,
      metadata: {
        priority: request.priority
      }
    };

    // Validate before processing
    const validation = await this.requestValidator.validateRequest(validationRequest);
    
    if (!validation.isValid) {
      return {
        success: false,
        error: {
          code: 'VALIDATION_FAILED',
          message: validation.errors.map(e => e.message).join(', '),
          provider: 'validator',
          retryable: false,
          details: validation.errors
        },
        metadata: {
          provider: 'validator',
          responseTime: validation.metadata.validationTime,
          cached: false,
          requestId: validation.metadata.requestId
        }
      };
    }

    // Apply optimization suggestions
    const optimizedRequest = this.applyOptimizations(request, validation.suggestions);
    
    // Proceed with validated and optimized request
    return this.executeRequest(optimizedRequest);
  }
}

Error Handling & Security

Validation Error Categories

1. Schema Errors
   • Missing required fields
   • Invalid data types
   • Format violations
   • Constraint violations
2. Security Errors
   • Injection attempts
   • Malicious payloads
   • Blocked content patterns
   • Unsafe input detection
3. Performance Errors
   • Rate limit exceeded
   • Payload size exceeded
   • Resource constraints
   • Optimization failures
4. Provider Errors
   • Unsupported model parameters
   • API version mismatches
   • Provider-specific violations
   • Capability mismatches

Security Implementation

class SecurityValidator {
  private sanitizer: DOMPurify;
  private sqlInjectionPatterns: RegExp[];
  private xssPatterns: RegExp[];

  async validate(request: ValidationRequest): Promise<SecurityValidationResult> {
    const errors: ValidationError[] = [];
    const warnings: ValidationWarning[] = [];
    const rulesApplied: string[] = ['security_validation'];

    // Check headers for security issues
    if (request.headers) {
      this.validateHeaders(request.headers, errors, warnings);
    }

    // Check body for security issues
    if (request.body) {
      await this.validatePayload(request.body, errors, warnings);
    }

    return { errors, warnings, rulesApplied };
  }

  private containsSqlInjection(input: string): boolean {
    const sqlPatterns = [
      /(\bunion\b.*\bselect\b)|(\bselect\b.*\bunion\b)/i,
      /(\bdrop\b.*\btable\b)|(\btable\b.*\bdrop\b)/i,
      /(\binsert\b.*\binto\b)|(\binto\b.*\binsert\b)/i,
      /(\bdelete\b.*\bfrom\b)|(\bfrom\b.*\bdelete\b)/i,
      /(\bupdate\b.*\bset\b)|(\bset\b.*\bupdate\b)/i,
      /('|(\\')|(;)|(--)|\||\*)/i
    ];
    
    return sqlPatterns.some(pattern => pattern.test(input.toLowerCase()));
  }

  private containsXss(input: string): boolean {
    const xssPatterns = [
      /<script[^>]*>.*?<\/script>/i,
      /javascript:/i,
      /on\w+\s*=/i,
      /<iframe[^>]*>/i,
      /<object[^>]*>/i,
      /<embed[^>]*>/i
    ];
    
    return xssPatterns.some(pattern => pattern.test(input.toLowerCase()));
  }
}

Performance Considerations

1. Validation Caching
   • Cache validation results for identical requests
   • Implement cache invalidation strategies
   • Use Redis or similar for distributed caching
2. Parallel Processing
   • Validate multiple requests concurrently
   • Use worker threads for CPU-intensive validation
   • Implement request queuing for high loads
3. Schema Optimization
   • Pre-compile JSON schemas for faster validation
   • Use efficient validation libraries
   • Implement schema versioning and caching
4. Memory Management
   • Limit memory usage for large payloads
   • Implement streaming validation for large requests
   • Clean up validation state regularly

Implementation Plan

Phase 1: Core Validation (Week 1-2)

1. Schema Validation
   • JSON Schema integration
   • Basic type checking
   • Required field validation
   • Error reporting system
2. Security Foundation
   • Input sanitization
   • Basic injection detection
   • Content filtering
   • Security error handling

Phase 2: Advanced Features (Week 3-4)

1. Performance Validation
   • Rate limiting implementation
   • Payload size controls
   • Optimization suggestions
   • Caching layer
2. Provider Integration
   • Provider-specific rules
   • Model capability validation
   • Custom validation logic
   • API version handling

Phase 3: Production Features (Week 5)

1. Optimization & Monitoring
   • Performance monitoring
   • Validation analytics
   • Cache optimization
   • Error trend analysis
2. Integration & Testing
   • API Connector integration
   • End-to-end testing
   • Load testing
   • Security testing

Dependencies

• Internal: API Connector Service, Metrics Service, Caching Service
• External: AJV (JSON Schema), DOMPurify, validation libraries
• Development: TypeScript 5+, Jest for testing, performance tools

Testing Strategy

1. Unit Tests
   • Schema validation accuracy
   • Security detection effectiveness
   • Performance limit enforcement
   • Error handling completeness
2. Integration Tests
   • End-to-end validation flows
   • API Connector integration
   • Provider-specific validation
   • Performance under load
3. Security Tests
   • Injection attack prevention
   • Malicious payload detection
   • Input sanitization verification
   • Security bypass attempts

Alternatives Considered

Client-Side Validation

• Approach: Validate requests in client applications
  • Pros: Faster feedback, reduced server load
  • Cons: Security risks, inconsistent implementation, bypass potential
  • Decision: Server-side validation provides better security and consistency

Third-Party Validation Services

• Approach: Use external validation services
  • Pros: Proven solutions, reduced development time
  • Cons: Vendor dependency, data privacy concerns, cost
  • Decision: Custom solution provides better control and integration

Middleware vs Service

• Approach: Implement as HTTP middleware
  • Pros: Automatic integration, transparent to clients
  • Cons: Less flexibility, harder to customize per provider
  • Decision: Service approach allows better customization and reusability

Open Questions

1. Custom Validation Rules: How should we support user-defined validation rules?
2. Performance Scaling: What are the performance requirements for high-volume validation?
3. Error Localization: Should error messages be localized for different regions?
4. Validation Versioning: How do we handle schema evolution and backward compatibility?
5. Real-time Updates: Should validation rules be updatable at runtime?
6. Compliance Integration: How do we integrate with compliance monitoring systems?

Appendix

Glossary

• JSON Schema: Standard for describing JSON document structure and constraints
• Input Sanitization: Process of cleaning and validating user input
• Rate Limiting: Technique to control the frequency of requests
• XSS: Cross-Site Scripting attack vector
• SQL Injection: Database attack through malicious SQL code
• Schema Validation: Process of verifying data against a predefined structure

References

• JSON Schema Specification
• OWASP Input Validation
• API Security Best Practices
• AJV JSON Schema Validator
• API Connector Service Specification

Revision History

• v0.1.0 (2025-08-12): Comprehensive specification with security and performance validation
• v0.0.0.1 (2025-08-09): Initial file creation