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Quickstart

Send your first LLMsRelay API request with Anthropic-compatible or OpenAI-compatible formats.

LLMsRelay is an independently operated API gateway. It is not affiliated with or endorsed by Anthropic, PBC. Product and model names are used only to describe compatibility.

Base URL: https://api.llmsrelay.com. Endpoint: POST /v1/messages. Auth header: x-api-key: YOUR_KEY. Default model: claude-opus-5-5. Time to first call: ~2 minutes.

01

Create a key

From your LLMsRelay dashboard

02

Send a request

Use Messages or Chat Completions

03

Connect your tools

Cursor, Claude Code, or your SDK

1. Get Your API Key

Sign up at llmsrelay.com and create an API key from your dashboard. Your key will look like sk-cs4-....

Validate gateway access

Before sending real requests, run two cheap checks: a health probe and a models list. They confirm the base URL, your network, and (for /v1/models) your API key — without spending any credits.

1. Liveness probe — /healthz

Public, unauthenticated. Returns 200 and a JSON status payload when the gateway is up. Use it from CI, monitoring, or any shell.

curl -sS -o /dev/null -w "HTTP %{http_code}\n" \
  https://api.llmsrelay.com/healthz

2. Auth + catalogue — /v1/models

Returns the list of model IDs you can use with the messages API. Requires a valid x-api-key. If this works, your key, base URL, and headers are all correct.

curl -sS https://api.llmsrelay.com/v1/models \
  -H "x-api-key: $ANTHROPIC_API_KEY" | jq '.data[].id'

2. Send Your First Request

curl https://api.llmsrelay.com/v1/messages \
  -H "x-api-key: YOUR_API_KEY" \
  -H "anthropic-version: 2023-06-01" \
  -H "content-type: application/json" \
  -d '{
    "model": "claude-opus-5-5",
    "max_tokens": 1024,
    "messages": [
      {"role": "user", "content": "What is the capital of France?"}
    ]
  }'

3. Set Up IDE Integration

Cursor

In Cursor Settings → Models → Add Provider:

  • Base URL: https://api.llmsrelay.com/v1
  • API Key: your LLMsRelay API key
  • Add a model ID returned by GET /v1/models, for example claude-opus-5-5

Claude Code

Claude Code CLI uses api.llmsrelay.com with sk-cs4-* keys. Use ANTHROPIC_API_KEY only — never ANTHROPIC_AUTH_TOKEN.

Linux / macOS:

Set environment variablesbash
export ANTHROPIC_BASE_URL="https://api.llmsrelay.com"
export ANTHROPIC_API_KEY="YOUR_SK_CS4_KEY"
export ANTHROPIC_MODEL="claude-opus-5-5"
export ANTHROPIC_SMALL_FAST_MODEL="claude-haiku-4.5"

Windows PowerShell:

Set environment variables (PowerShell)powershell
$env:ANTHROPIC_BASE_URL = "https://api.llmsrelay.com"
$env:ANTHROPIC_API_KEY = "YOUR_SK_CS4_KEY"
$env:ANTHROPIC_MODEL = "claude-opus-5-5"
$env:ANTHROPIC_SMALL_FAST_MODEL = "claude-haiku-4.5"

4. List Available Models

List the model IDs currently available to your key:

curl https://api.llmsrelay.com/v1/models \
  -H "Authorization: Bearer YOUR_API_KEY"

Free model API offers

See the current free API offer pages for supported model IDs and setup examples:

5. Billing Basics

  • Choose a one-time platform usage pack. Current prices and credited usage are shown on the Plans page.
  • You are billed per token (input + output) based on the model used
  • Check your balance anytime in the dashboard
  • Purchased usage remains available until it is consumed

Next Steps

Ready to start?

Create a key and configure a compatible API route in under 2 minutes.

View Plans