Metadata

@dataclass
class CallEvent:
    ts: str             # ISO 8601 UTC timestamp
    model: str          # model name from response
    provider: str       # anthropic | openai | groq | unknown
    input_tokens: int
    output_tokens: int
    cost_usd: float     # estimated cost
    latency_ms: int
    user_id: str | None
    session_id: str | None
    tags: list[str] | None
    routed_tier: str | None   # set by Router if routing was used
    error: str | None         # set if the call raised an exception