Messages API

Anthropic-native chat completions. 100% identical request/response shape; tool_choice is the only normalization layer.

Request

POST https://api.oneprovider.dev/v1/messages
x-api-key: sk-...
anthropic-version: 2023-06-01
content-type: application/json
{
"model": "claude-sonnet-5-5",
"max_tokens": 1024,
"system": "You are a concise assistant.",
"messages": [
{"role": "user", "content": "Why is the sky blue?"}
]
}

Request body

Prompt caching

Mark up to four cache breakpoints with cache_control: {"type": "ephemeral"} on text or system blocks. Cached tokens are billed at 10% of the normal input rate for most models (and the response reports cache_read_input_tokens in usage).

{
"model": "claude-sonnet-5-5",
"max_tokens": 1024,
"system": [
{
"type": "text",
"text": "Long stable system prompt that should be cached...",
"cache_control": {"type": "ephemeral"}
}
],
"messages": [{"role": "user", "content": "Question 1"}]
}

Response

{
"id": "msg_01XYZ...",
"type": "message",
"role": "assistant",
"model": "claude-sonnet-5-5",
"content": [
{"type": "text", "text": "Rayleigh scattering — short wavelengths..."}
],
"stop_reason": "end_turn",
"usage": {
"input_tokens": 48,
"output_tokens": 92,
"cache_creation_input_tokens": 0,
"cache_read_input_tokens": 0
}
}

Quick answers

Which base URL do I use?

Claude Code and Anthropic SDKs use https://api.oneprovider.dev. OpenAI SDKs and OpenAI-compatible clients use https://api.oneprovider.dev/v1. One key works behind both; the model list is on the models page ; rates are on the pricing page .

How do I authenticate?

Send the raw sk-… key in x-api-key or Authorization: Bearer: one of them, never both. Keep the key in an environment variable, not in a file that gets committed. More on authentication .

Where do I get a key?

Open your cabinet in the Telegram bot @oneprovider_robot or at app.oneprovider.dev, top up the balance and press “Issue a key”. Each key can carry its own spend limit. Cabinet & API keys .

What do 401, 404 and 429 mean?

401: the key is missing, mistyped or sent in the wrong header; paste the whole key without quotes or spaces. 404: usually a wrong base URL, for example a missing or doubled /v1. 429 with “Insufficient balance”: the cabinet balance or the key’s spend limit is used up, so top up instead of retrying; any other 429 is a rate limit, so wait for Retry-After. Details: error codes and troubleshooting .

Why do streams cut off or reset?

VPN and VLESS proxies often buffer SSE or break HTTP/2 negotiation. OneProvider has no regional restrictions and does not buffer streams, so turn the proxy off and retry.

Where do I ask if this is not enough?

Message @Oneproviderhelpbot on Telegram or open “Support” in the web cabinet, with the HTTP status code and the exact error message. How support works .