Metrics & Cost Tracking
Patter automatically tracks cost and latency for every call, broken down by provider component (STT, TTS, LLM, telephony).
How It Works
Metrics are collected automatically during calls. When a call ends, the on_call_end callback receives a CallMetrics object with the full breakdown:
async def on_call_end(event):
metrics = event.get("metrics")
if metrics:
print(f"Duration: {metrics.duration_seconds}s")
print(f"Total cost: ${metrics.cost.total:.4f}")
print(f" STT: ${metrics.cost.stt:.4f}")
print(f" TTS: ${metrics.cost.tts:.4f}")
print(f" LLM: ${metrics.cost.llm:.4f}")
print(f" Telephony: ${metrics.cost.telephony:.4f}")
print(f"Avg latency: {metrics.latency_avg.total_ms}ms")
print(f"P95 latency: {metrics.latency_p95.total_ms}ms")
Cost Breakdown
The CostBreakdown object provides per-component costs in USD:
| Field | Description |
|---|
stt | Speech-to-text cost (Deepgram, Whisper). |
tts | Text-to-speech cost (ElevenLabs, OpenAI TTS). |
llm | LLM cost (OpenAI Realtime tokens). |
telephony | Telephony cost (Twilio, Telnyx per-minute). |
total | Sum of all components. |
Latency Breakdown
The LatencyBreakdown object provides per-component latency in milliseconds:
| Field | Description |
|---|
stt_ms | Time from user speech to transcript. |
llm_ms | Time from transcript to LLM response. |
tts_ms | Time from LLM response to first audio byte. |
total_ms | End-to-end latency (user speech to first audio). |
latency_avg and latency_p95 are available on CallMetrics.
Per-Turn Metrics
Each conversation turn is tracked individually:
async def on_call_end(event):
metrics = event.get("metrics")
if metrics:
for turn in metrics.turns:
print(f"Turn {turn.turn_index}:")
print(f" User: {turn.user_text}")
print(f" Agent: {turn.agent_text}")
print(f" Latency: {turn.latency.total_ms}ms")
Custom Pricing
Override default provider pricing estimates:
phone = Patter(
openai_key="sk-...",
mode="local",
pricing={
"deepgram": {"price": 0.005}, # Override STT price per minute
"elevenlabs": {"price": 0.15}, # Override TTS price per 1k chars
"twilio": {"price": 0.015}, # Override telephony price per minute
},
)
Default Pricing
| Provider | Unit | Default Price |
|---|
| Deepgram | per minute | $0.0043 |
| Whisper | per minute | $0.006 |
| ElevenLabs | per 1k chars | $0.18 |
| OpenAI TTS | per 1k chars | $0.015 |
| OpenAI Realtime | per token | varies by type |
| Twilio | per minute | $0.013 |
| Telnyx | per minute | $0.007 |
Default pricing is based on publicly listed provider rates and may become stale. Pass your own overrides for accurate cost tracking, or check the provider’s pricing page.
Real-Time Metrics
Use the on_metrics callback for live cost updates during a call:
async def on_metrics(data):
cost = data.get("cost_so_far")
if cost:
print(f"Running cost: ${cost['total']:.4f}")
await phone.serve(
agent,
port=8000,
on_metrics=on_metrics,
)
Data Types
from patter import CallMetrics, CostBreakdown, LatencyBreakdown, TurnMetrics
CallMetrics
| Field | Type | Description |
|---|
call_id | str | Unique call identifier. |
duration_seconds | float | Total call duration. |
turns | tuple[TurnMetrics, ...] | Per-turn metrics. |
cost | CostBreakdown | Cost breakdown. |
latency_avg | LatencyBreakdown | Average latency. |
latency_p95 | LatencyBreakdown | 95th percentile latency. |
provider_mode | str | Voice mode used. |
stt_provider | str | STT provider name. |
tts_provider | str | TTS provider name. |
telephony_provider | str | Telephony provider name. |
TurnMetrics
| Field | Type | Description |
|---|
turn_index | int | Zero-based turn index. |
user_text | str | What the user said. |
agent_text | str | What the agent replied. |
latency | LatencyBreakdown | Latency for this turn. |
stt_audio_seconds | float | Audio duration processed by STT. |
tts_characters | int | Characters synthesized by TTS. |
timestamp | float | Unix timestamp. |
