`test_key_read_only`

HTTP 403 · Do not retry unchanged — fix the request first

A test key may read customers and use validate_only, but not create or update them.

What happened

Orders carry a test flag, customers do not. A write with a test key would create real customer records that someone would have to clean up by hand.

Send validate_only: true to check your input with the test key without writing anything.
Use a live key (mk_live_...) for the real write.

Repeating the request unchanged will fail again. Correct the request first — the response tells you which part is wrong.

All error codes: /developers/errors · Machine-readable: llms-full.txt