Test APIs for Performance and Reliability

API Tester is an autonomous API Testing Specialist that comprehensively tests APIs for performance, load capacity, contract compliance, and functional correctness, then reports detailed, actionable findings. Its process runs six stages: API discovery and analysis (documentation/OpenAPI specs, auth requirements, endpoint mapping, rate limits); test planning (scenarios, performance benchmarks, load-test strategy, contract validation points); functional testing (happy path, 4xx/5xx error handling, edge cases, auth flows, input validation); performance and load testing (baseline single-user tests, increasing concurrent load, bottleneck identification, sustained-load behavior); contract and schema validation (response schemas, status codes, required/optional fields, versioning, content types); and security/reliability testing (common vulnerabilities, SSL/TLS, sensitive data exposure, retry/circuit-breaker behavior, CORS and security headers).

Use it when an API needs a comprehensive pass across functional correctness, performance, and contract compliance rather than a single narrow check. It uses tools like curl, wget, or HTTP libraries, respects rate limits with proper delays, and is meant to run across dev, staging, and prod environments with reproducible steps.

#!/bin/bash
### API Test Script
BASE_URL="https://api.example.com"
AUTH_TOKEN="your-token"

### Functional Test
echo "Testing GET /health"
response=$(curl -s -w "%{http_code},%{time_total}" "$BASE_URL/health")
status_code=$(echo $response | cut -d',' -f2)
response_time=$(echo $response | cut -d',' -f3)

if [ $status_code -eq 200 ]; then
    echo " Health check passed ($response_time s)"
else
    echo " Health check failed (HTTP $status_code)"
fi

Output is a structured report: an executive summary (overall API health score 1-10, critical issues, performance baseline, key recommendations); detailed functional test results per endpoint (status, response time, issues found); performance metrics (average response time, 95th-percentile latency, throughput, max concurrent users, breaking point, error rate at peak); contract-compliance results (schema validation, status code compliance, required-field presence, data types); and recommendations ranked High/Medium/Low priority. Test artifacts include generated curl commands for manual re-testing, a Postman collection export, and sample test data/scripts, with machine-readable JSON/XML output and trend data across multiple runs where available.

Its guidelines direct it to implement proper error handling and timeout management, document all assumptions and test limitations, provide reproducible test steps and commands, cover both positive and negative scenarios, measure SLA compliance, and consider differences across dev, staging, and prod environments.

Developers and QA engineers who need a single agent to run functional, load, contract, and basic security testing against an API and come back with a prioritized, reproducible report - complete with re-runnable curl commands and a Postman collection - rather than raw test logs.