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AnyRouter

Using Responses API

Use AnyRouter's Responses endpoint for modern agent and tool workflows with structured output items.

Use the Responses endpoint when your application benefits from a single response envelope with typed output items, tool calls, and optional reasoning metadata. This guide is for agent and tool builders deciding between endpoints, and shows a minimal working request.

Before you start

  • An AnyRouter API key (prefixed sk-ar-). Create one in the dashboard.
  • The OpenAI SDK, or any HTTP client — the Responses endpoint is OpenAI-compatible.

When to use Responses

Use caseRecommended endpoint
Existing OpenAI chat appChat Completions
Anthropic Messages clientMessages
Agent or tool workflowResponses
Model and price discoveryModels

Reach for Responses when you want tool calls and reasoning kept in one typed output array — it makes multi-step agent loops easier to track than parsing chat deltas.

Minimal request

The Responses endpoint uses the same base URL and key as Chat Completions:

import OpenAI from "openai"

const client = new OpenAI({
  baseURL: "https://anyrouter.dev/api/v1",
  apiKey: process.env.ANYROUTER_API_KEY,
})

const response = await client.responses.create({
  model: "openai/gpt-5.4-mini",
  input: "Turn these notes into three action items.",
})

console.log(response.output_text)

curl https://anyrouter.dev/api/v1/responses \
  -H "Authorization: Bearer sk-ar-your-key" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "openai/gpt-5.4-mini",
    "input": "Turn these notes into three action items."
  }'

Add tools for agent loops

Responses keeps tool calls in the output array, which makes multi-step agent loops easier to track:

{
  "model": "openai/gpt-5.4-mini",
  "input": "Find the status of order 1234.",
  "tools": [
    {
      "type": "function",
      "name": "lookup_order",
      "description": "Look up an order by id",
      "parameters": {
        "type": "object",
        "properties": {
          "order_id": { "type": "string" }
        },
        "required": ["order_id"]
      }
    }
  ],
  "tool_choice": "auto"
}

Routing preferences

Responses accepts the same AnyRouter provider object as Chat Completions:

{
  "provider": {
    "sort": "latency",
    "allow_fallbacks": true,
    "max_price": {
      "prompt": "2.00",
      "completion": "8.00"
    }
  }
}

See Provider Routing for every field.

Verify

Send the minimal request above and confirm output_text (TypeScript) or a populated output array (curl) comes back.

Troubleshooting

output_text is empty but there was a tool call

When the model calls a tool, the answer lives in the output array as a tool-call item, not in output_text. Run the tool, append the result, and call again to get the final text.