Skip to main content
The Chat Completions API supports routing directly at the request level, without needing to create a router. You can use it to call a specific model, add fallbacks, or let the engine auto-select the best model, all in a single request. Request-level routing can be a good fit if you:
  • Want to call a specific model through a unified API without setting up a router
  • Are prototyping or benchmarking before committing to a router configuration
For more advanced use cases like conditional routing, A/B testing with weighted variants, or shared prompt templates, we recommend setting up a router.

​
Direct model call

Specify a model directly by its provider/model identifier: 
curl -X POST https://api.inworld.ai/v1/chat/completions \
  -H 'Authorization: Bearer <your-api-key>' \
  -H 'Content-Type: application/json' \
  -d '{
    "model": "openai/gpt-5.2",
    "messages": [{ "role": "user", "content": "Hello!" }]
  }'
This sends the request to the specified model with no routing logic. You still benefit from Inworld Router’s unified API.

​
Fallbacks

Add fallback models via extra_body.models. If the primary model fails, the router automatically tries the next model in the list: 
curl -X POST https://api.inworld.ai/v1/chat/completions \
  -H 'Authorization: Bearer <your-api-key>' \
  -H 'Content-Type: application/json' \
  -d '{
    "model": "openai/gpt-5.2",
    "messages": [{ "role": "user", "content": "Hello!" }],
    "extra_body": {
      "models": ["anthropic/claude-opus-4-6", "google-ai-studio/gemini-2.5-pro"]
    }
  }'
In this example, the router tries gpt-5.2 first, then Claude Opus, then Gemini Pro. You can inspect which models were attempted in the metadata.attempts array of the response.

​
Auto model selection

Set model to auto and provide sorting criteria via extra_body.sort to let the router pick the best model automatically: 
curl -X POST https://api.inworld.ai/v1/chat/completions \
  -H 'Authorization: Bearer <your-api-key>' \
  -H 'Content-Type: application/json' \
  -d '{
    "model": "auto",
    "messages": [{ "role": "user", "content": "Hello!" }],
    "extra_body": {
      "sort": ["price"]
    }
  }'
This selects the cheapest available model. Available sort criteria: price, latency, throughput, intelligence, math, coding. You can combine multiple criteria — models are ranked by the first criterion, with subsequent criteria used as tiebreakers: 
curl -X POST https://api.inworld.ai/v1/chat/completions \
  -H 'Authorization: Bearer <your-api-key>' \
  -H 'Content-Type: application/json' \
  -d '{
    "model": "auto",
    "messages": [{ "role": "user", "content": "Hello!" }],
    "extra_body": {
      "sort": ["price", "latency"]
    }
  }'
This picks the cheapest model, using latency as a tiebreaker.

​
Filtering models

Use extra_body.models to restrict the candidate pool, or extra_body.ignore to exclude specific models or entire providers: 
{
  "model": "auto",
  "messages": [{ "role": "user", "content": "Hello!" }],
  "extra_body": {
    "models": ["openai/gpt-5.2", "anthropic/claude-opus-4-6", "google-ai-studio/gemini-2.5-pro"],
    "sort": ["latency"]
  }
}