OpenAI-compatible API

Milly Lab API

The Milly Lab API is an OpenAI-compatible REST API at https://api.m-lab.app/v1. One key reaches 13 chat models from OpenAI, Anthropic, Google, DeepSeek and xAI, 4 image models and an embeddings model. It comes with the Max plan ($42 a month) and higher. A call costs the provider's rate plus $1 per million input or output tokens.

Last updated: 2026-10-04

Milly Lab API at a glance

How do I make my first request?

Create a key under API keys in your Milly Lab account, then point any OpenAI SDK at https://api.m-lab.app/v1. Each example below sends the same chat request.

1. Create a key. It starts with mk_ and is shown only once, so store it in an environment variable such as MILLY_API_KEY.
2. Set the base URL to https://api.m-lab.app/v1. Nothing else changes in OpenAI-compatible code.
3. Pick a model id from GET /v1/models, for example claude-sonnet-5.

curl https://api.m-lab.app/v1/chat/completions \
  -H "Authorization: Bearer $MILLY_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model": "claude-sonnet-5", "messages": [{"role": "user", "content": "Hello"}]}'

import os
from openai import OpenAI

client = OpenAI(base_url="https://api.m-lab.app/v1", api_key=os.environ["MILLY_API_KEY"])
r = client.chat.completions.create(
    model="claude-sonnet-5",
    messages=[{"role": "user", "content": "Hello"}],
)
print(r.choices[0].message.content)

import OpenAI from "openai";

const client = new OpenAI({ baseURL: "https://api.m-lab.app/v1", apiKey: process.env.MILLY_API_KEY });
const r = await client.chat.completions.create({
  model: "claude-sonnet-5",
  messages: [{ role: "user", content: "Hello" }],
});
console.log(r.choices[0].message.content);

The response is a standard chat.completion object, and its usage field shows the tokens you were billed for. Send stream: true to receive the answer as server-sent events instead.

Which endpoints does the API have?

All 5 API endpoints live under https://api.m-lab.app/v1.

Which plans include API access?

API access is included in the Max, Advanced and Enterprise plans. On Free, Starter and Pro you cannot create API keys. If your plan drops below Max, existing keys stop working until you upgrade, but you can still see and revoke them.

The Free plan gives 10 chat messages per model every 4 hours in the web app, without API access.

Compare all plans

How much does an API call cost?

An API call costs the provider's rate for the model plus a Milly Lab platform fee of $1 per million input tokens and $1 per million output tokens; image generation adds $0.01 per image. Your plan's monthly allowance for the model pays first, and anything beyond it comes from your top-up balance at 2× the price.

• Plan allowance first: a model your plan allocates is paid from that model's monthly allowance at the listed price.
• Then the top-up balance at 2×: other models, and usage after the allowance runs out, cost 2× the listed price.
• Checked before the call: if allowance and balance cannot cover a request, the API answers 402 before any provider is called, so nothing is billed.
• Partial output is billed: if your client disconnects mid-stream, generation finishes and the tokens produced are charged.

Worked example

A Claude Sonnet 5 request with 10,000 input tokens and 1,000 output tokens costs $0.041 from the plan allowance (10,000 × $3.00 + 1,000 × $11.00 per million tokens) or $0.082 from the top-up balance.

Prices are in US dollars. Payments are processed by SmartPay, a payment system from Tajikistan, and can be made in any currency.

Which models can I call, and at what price?

These are the models GET /v1/models listed on 2026-10-04: chat models, image models and one embeddings model. Prices include the $1 platform fee; the endpoint itself is always the current source.

Chat models

Image models

Embeddings

text-embedding-3-small returns 1,536-dimension vectors and costs $1.02 per million input tokens including the fee. No plan includes embeddings, so they are always paid from the top-up balance at 2×.

The Plan allowance column names the plans that include a monthly allowance for the model. Models marked “Balance only”, such as Grok 4.6, have no plan allowance and are paid from the top-up balance at 2×. Enterprise allowances are agreed per contract. Other image quality levels change the per-image price.

What are the rate limits?

Each API key can make up to 120 requests per minute, and an account can hold up to 5 active keys. A request over the limit gets HTTP 429 with a Retry-After header that says how many seconds to wait.

Every /v1 response carries an x-request-id header; quote it when you contact support. Responses to a request with a valid key also carry x-ratelimit-limit, x-ratelimit-remaining and x-ratelimit-window.

How do spend caps and allowed models work?

Each key can have a monthly spend cap in US dollars and a list of allowed models. A call after the cap is reached returns 402 spend_cap_reached; a call to a model outside the list returns 403 model_not_allowed. Both checks run before anything is charged.

CORS is open on /v1, so browser code can call the API directly, but a key in a web page is visible to every visitor. Give such a key a tight spend cap and an allowed-model list, or call the API from your own server.

What error codes does the API return?

Errors use the OpenAI error format shown below, so SDK error handling works unchanged. Branch on the code field, not on the message text.

{"error": {"message": "…", "type": "…", "code": "…"}}

Questions developers ask

Where is the full API reference?

The API guide covers streaming, embeddings, images, the usage endpoint and best practices in detail.