Create a message

Adds a message to a thread's message stack. Supports user, system, tool, and assistant roles. Cannot add messages to threads created via Chat Completions. Tool messages must follow an assistant message whose tool_call_id matches. System messages should be the first message in a thread.

curl -X POST "https://example.com/v1/threads/497f6eca-6276-4993-bfeb-53cbbbba6f08/messages" \  -H "Content-Type: application/json" \  -d '{    "content": "Welche Kündigungsfristen gelten während der Probezeit?",    "role": "user"  }'

{  "content": "Welche Kündigungsfristen gelten während der Probezeit?",  "created_at": "2025-03-15T09:12:45.123456Z",  "id": "4d5e6f70-8901-cdef-0123-445566778899",  "role": "user",  "thread_id": "1a2b3c4d-5678-9abc-def0-112233445566"}