Build with Echo

Send an Echo API key as a bearer token on every request. Create a key from the API keys page; the complete secret is shown only once.

Authorization: Bearer ECHO_API_KEY

These examples call the same text completion endpoint. SDK examples disable automatic retries so your application can handle failures and idempotency intentionally.

curl --fail-with-body --silent --show-error \
  https://echo.tracerml.ai/v1/chat/completions \
  -H "Authorization: Bearer ${ECHO_API_KEY}" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "echo",
    "messages": [
      {"role": "user", "content": "Explain recursion in one sentence."}
    ],
    "max_tokens": 128
  }'

import os
from openai import OpenAI

client = OpenAI(
    api_key=os.environ["ECHO_API_KEY"],
    base_url="https://echo.tracerml.ai/v1",
    timeout=600.0,
    max_retries=0,
)

completion = client.chat.completions.create(
    model="echo",
    messages=[
        {"role": "user", "content": "Explain recursion in one sentence."}
    ],
    max_tokens=128,
)

print(completion.choices[0].message.content)

import OpenAI from "openai";

const client = new OpenAI({
  apiKey: process.env.ECHO_API_KEY,
  baseURL: "https://echo.tracerml.ai/v1",
  timeout: 600_000,
  maxRetries: 0,
});

const completion = await client.chat.completions.create({
  model: "echo",
  messages: [
    { role: "user", content: "Explain recursion in one sentence." },
  ],
  max_tokens: 128,
});

console.log(completion.choices[0].message.content);

Personal subscription credit and one-time top-ups fund the same USD balance. Use that balance in first-party Chat or through an API key, and select the model lane for each request.

The dashboard balance is authoritative. Token counts remain visible for usage analysis, but they are not a separate wallet or invoice calculation.

Send a JSON object with a non-empty message history containing at least one user message. Conversations are stateless; include the history needed for each request.

A successful non-streaming request returns one assistant message. Read the answer from choices[0].message.content and retain the X-Tracer-Request-ID response header for support.

{
  "id": "chatcmpl-...",
  "object": "chat.completion",
  "created": 1780000000,
  "model": "echo",
  "choices": [{
    "index": 0,
    "message": {
      "role": "assistant",
      "content": "Recursion solves a problem by reducing it to smaller instances of itself."
    },
    "finish_reason": "stop"
  }],
  "usage": {
    "prompt_tokens": 18,
    "completion_tokens": 14,
    "total_tokens": 32
  }
}

Usage and cost fields

The standard usage object reports prompt, completion, and total tokens. It does not include a cost field, and token counts should not be treated as an invoice calculation.

For raw streaming clients, the optional X-Tracer-Progress: 1 header can add a tracer.usage event after a successful completion. Its usage payload may include:

Cost events are optional. Use the account dashboard as the source for usage and billing records.

Set stream: true. Echo responds with text/event-stream; append each choices[0].delta.content value in order and stop when you receive data: [DONE].

data: {"id":"chatcmpl-...","object":"chat.completion.chunk","model":"echo","choices":[{"index":0,"delta":{"role":"assistant","content":"One"},"finish_reason":null}]}

data: {"id":"chatcmpl-...","object":"chat.completion.chunk","model":"echo","choices":[{"index":0,"delta":{},"finish_reason":"stop"}]}

data: [DONE]

Application errors normally use an OpenAI-shaped error envelope. Framework validation failures, including malformed JSON or a missing body, may use a different 422 response shape.

{
  "error": {
    "message": "messages must be a non-empty array",
    "type": "invalid_request_error",
    "param": "messages",
    "code": "invalid_request"
  }
}

Echo enforces request-rate limits and may apply account-specific concurrency and daily request limits. Limits are attributed to the tenant associated with the API key and can vary by deployment or account.

• On 429, honor the Retry-After response header when present.
• Otherwise use exponential backoff with jitter and a bounded retry count.
• Do not retry validation, authentication, billing, or policy failures unchanged.
• Monitor status, latency, interrupted streams, and X-Tracer-Request-ID.