Every ICON node provides JSON-RPC APIs. To talk to an ICON node, you can send raw JSON-RPC request, or, even better, use ICON SDKs in various languages. ICON officially supports Java, Python, JavaScript, and Swift.

Also, T-Bears provides CLI commands implementing JSON-RPC APIs. T-Bears CLI is a handy tool to test your score quickly without a single line of code during initial test.

Besides, there are couple of community driven tools.