Send messages to an LLM and receive a completion. Requires authenticated user with active organization. Usage is tracked for auditing and future quota enforcement.

Message Roles:

• system: Defines the AI's behavior and constraints (e.g., "You are a helpful coding assistant"). Place at the beginning of the conversation. Only one system message is supported (Gemini limitation).
• user: Represents the human's questions or requests. Can appear multiple times in the conversation.
• assistant: Represents the AI's previous responses. Used to maintain conversation history and context.

Example conversation flow:

{
  "messages": [
    {"role": "system", "content": "You are a helpful assistant that responds in French."},
    {"role": "user", "content": "What is the capital of France?"},
    {"role": "assistant", "content": "La capitale de la France est Paris."},
    {"role": "user", "content": "What is its population?"}
  ]
}

The AI will remember the conversation context and respond about Paris's population.