API Testing

Enter your own API key, pick an endpoint type and a model, write the message you want to send, and all five snippets below update together. Copy one and run it, or press Send request — your browser calls the gateway directly, so neither the key nor the response passes through the docs site. There is no base URL to fill in: the docs site is served by the gateway itself, and the samples already point at it.

“Send request” is a real call: it spends tokens from your account and is billed by actual usage. Copying the code costs nothing.

API key

Endpoint type ChatResponsesClaudeGemini

Model

Response mode Non-streaming Streaming

Message Explain what an API gateway is, in one sentence.

Your key stays in this browser tab, is cleared when you close it, and is never sent to the docs site.

POST /v1/chat/completions

cURL Python Node.js Go Java

curl https://llm.usmm.cn/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -d '{
    "model": "deepseek-v4.1-flash",
    "messages": [{ "role": "user", "content": "Explain what an API gateway is, in one sentence." }]
  }'

import requests

response = requests.post(
    "https://llm.usmm.cn/v1/chat/completions",
    headers={
        "Content-Type": "application/json",
        "Authorization": "Bearer YOUR_API_KEY",
    },
    json={
      "model": "deepseek-v4.1-flash",
      "messages": [{ "role": "user", "content": "Explain what an API gateway is, in one sentence." }]
    },
    timeout=60,
)
response.raise_for_status()
print(response.json())

const response = await fetch("https://llm.usmm.cn/v1/chat/completions", {
  method: "POST",
  headers: {
    "Content-Type": "application/json",
    "Authorization": "Bearer YOUR_API_KEY",
  },
  body: JSON.stringify({
    "model": "deepseek-v4.1-flash",
    "messages": [{ "role": "user", "content": "Explain what an API gateway is, in one sentence." }]
  }),
});

console.log(await response.json());

package main

import (
	"fmt"
	"io"
	"net/http"
	"strings"
)

func main() {
	payload := `{
  "model": "deepseek-v4.1-flash",
  "messages": [{ "role": "user", "content": "Explain what an API gateway is, in one sentence." }]
}`

	req, err := http.NewRequest(http.MethodPost, "https://llm.usmm.cn/v1/chat/completions", strings.NewReader(payload))
	if err != nil {
		panic(err)
	}
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Authorization", "Bearer YOUR_API_KEY")

	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		panic(err)
	}
	defer resp.Body.Close()

	out, err := io.ReadAll(resp.Body)
	if err != nil {
		panic(err)
	}
	fmt.Println(string(out))
}

import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;

var payload = """
{
  "model": "deepseek-v4.1-flash",
  "messages": [{ "role": "user", "content": "Explain what an API gateway is, in one sentence." }]
}
""";

var request = HttpRequest.newBuilder()
        .uri(URI.create("https://llm.usmm.cn/v1/chat/completions"))
        .header("Content-Type", "application/json")
        .header("Authorization", "Bearer YOUR_API_KEY")
        .POST(HttpRequest.BodyPublishers.ofString(payload))
        .build();

var response = HttpClient.newHttpClient()
        .send(request, HttpResponse.BodyHandlers.ofString());

System.out.println(response.body());

Copy Send request

Response

Nothing sent yet. Copy the code above and run it, or send the request from here and read the real response.

Full API documentation

The four endpoint types above cover the protocol dialects the gateway speaks. They differ in two places:

• The auth header. Chat and Responses use Authorization, Claude uses x-api-key, Gemini uses x-goog-api-key. This is what trips people up when switching dialects.
• How streaming is expressed. The first three put "stream": true in the request body; Gemini’s native format changes the action in the URL (:streamGenerateContent).

The gateway serves more than these four. The full list is below, with parameters, request bodies and response examples, and you can try any of them here. The prose version of the same material lives in Using the API & Playground, which reads better end to end.

Loading the API documentation…