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Every API response from ARouter includes detailed usage information. This lets you track costs and token consumption in real time without making additional API calls.

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Usage in Responses

The usage object is returned in every non-streaming response (and in the final chunk of streaming responses): 
{
  "id": "gen-abc123",
  "model": "openai/gpt-5.4",
  "usage": {
    "prompt_tokens": 120,
    "completion_tokens": 85,
    "total_tokens": 205,
    "prompt_tokens_details": {
      "cached_tokens": 60,
      "audio_tokens": 0
    },
    "completion_tokens_details": {
      "reasoning_tokens": 30,
      "audio_tokens": 0,
      "accepted_prediction_tokens": 0,
      "rejected_prediction_tokens": 0
    }
  }
}

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Token Fields

FieldDescription
prompt_tokensTotal input tokens (includes cached tokens)
completion_tokensTotal output tokens (includes reasoning tokens)
total_tokensSum of prompt + completion tokens
prompt_tokens_details.cached_tokensTokens served from the provider’s prompt cache
completion_tokens_details.reasoning_tokensTokens used for internal reasoning (thinking models)
completion_tokens_details.accepted_prediction_tokensSpeculative decoding tokens accepted
completion_tokens_details.rejected_prediction_tokensSpeculative decoding tokens rejected

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Cost Tracking

ARouter bills based on the actual token counts reported by the upstream provider. Pricing is passed through at cost — no inference markup. To calculate exact cost: 
cost = (prompt_tokens × input_price_per_token) + (completion_tokens × output_price_per_token)
Cached tokens are typically billed at a reduced rate (often 50% of the standard input price). See Prompt Caching for details.

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Streaming Usage

In streaming mode, the final SSE chunk includes the full usage object with empty choices: 
{
  "id": "gen-abc123",
  "choices": [],
  "usage": {
    "prompt_tokens": 120,
    "completion_tokens": 85,
    "total_tokens": 205
  }
}
Enable streaming usage by passing stream_options: { include_usage: true } in your request.

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Dashboard Reporting

All usage data is visible in the Activity page with filtering by:
  • Time period (1 hour → 1 year)
  • Grouping (Model, API Key, Creator)
Export as CSV or PDF for accounting and budget planning. See Activity Export.

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API Access

Retrieve transaction history and balance programmatically: 
# Get current balance
curl https://api.arouter.ai/v1/billing/balance \
  -H "Authorization: Bearer $AROUTER_API_KEY"

# List recent transactions
curl https://api.arouter.ai/v1/billing/transactions \
  -H "Authorization: Bearer $AROUTER_API_KEY"