Charles Proxy - HTTP proxy / HTTP monitor / Reverse Proxy
ifttt - IFTTT puts the internet to work for you. Create simple connections between the products you use every day.
Wireshark - Wireshark is a network protocol analyzer for Unix and Windows. It lets you capture and interactively browse the traffic running on a computer network.
Zapier - Connect the apps you use everyday to automate your work and be more productive. 1000+ apps and easy integrations - get started in minutes.
Postman - The Collaboration Platform for API Development
n8n.io - Free and open fair-code licensed node based Workflow Automation Tool. Easily automate tasks across different services.