Inference

Messages

Anthropic's Messages API, for the Anthropic SDK and the tools built on it. The key may also come in x-api-key. Errors keep Anthropic's error body.

POST/api/v1/messagesTry it

Your key

Request

curl -X POST https://api.llm.buzz/api/v1/messages \
  -H "Authorization: Bearer $LLM_BUZZ_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "model": "anthropic/claude-haiku-5.5",
  "max_tokens": 256,
  "messages": [
    {
      "role": "user",
      "content": "Say hello in one word."
    }
  ]
}'

import os
from anthropic import Anthropic

client = Anthropic(base_url="https://api.llm.buzz/api", api_key=os.environ["LLM_BUZZ_KEY"])
message = client.messages.create(
    model="anthropic/claude-haiku-5.5",
    max_tokens=256,
    messages=[{"role": "user", "content": "Say hello in one word."}],
)
print(message.content[0].text)

import Anthropic from "@anthropic-ai/sdk";

const client = new Anthropic({ baseURL: "https://api.llm.buzz/api", apiKey: process.env.LLM_BUZZ_KEY });
const message = await client.messages.create({
  model: "anthropic/claude-haiku-5.5",
  max_tokens: 256,
  messages: [{ role: "user", content: "Say hello in one word." }],
});

Response

{
  "id": "msg_...",
  "type": "message",
  "role": "assistant",
  "model": "anthropic/claude-haiku-5.5",
  "content": [
    {
      "type": "text",
      "text": "Hello!"
    }
  ],
  "stop_reason": "end_turn",
  "usage": {
    "input_tokens": 14,
    "output_tokens": 4,
    "cache_creation_input_tokens": 0,
    "cache_read_input_tokens": 0,
    "cost": 0.0000034
  }
}

{
  "type": "error",
  "error": {
    "type": "invalid_request_error",
    "message": "..."
  }
}

{
  "type": "error",
  "error": {
    "type": "authentication_error",
    "message": "A valid API key is required: send x-api-key or Authorization: Bearer."
  }
}

Authorization

An inference key, as Authorization: Bearer KEY or in x-api-key, the header the Anthropic SDK sends.

Keys and limits

Parameters

x-session-idstringheader
Names the conversation, as session_id does, so its turns stay on the provider that holds its cache.

Body application/json

modelstringrequired
A model's name from GET /api/v1/models, such as deepseek/deepseek-v4.1-flash. A suffix changes one request: :floor tries the cheapest provider first and :nitro the fastest. On Chat Completions and Responses :online asks for a web search, which llm.buzz does not run today: the request is served without one and x-sgr-ignored-parameters names web_search->dropped(search_unavailable), or for an organization whose requests llm.buzz keeps in the EU it answers 400 web_search_unavailable_in_region. On Messages :online does nothing and is named as model:online.
max_tokensintegerrequired
The most tokens the answer may use.
messagesobject[]required
The conversation, as Anthropic's message objects.
systemstring or object[]
The system prompt: a string, or a list of text blocks, which may carry cache_control.
streambooleandefault false
Stream Anthropic's server-sent events.
toolsobject[]
Tools in Anthropic's shape. {"type": "tool_search_tool_bm25"} or {"type": "tool_search_tool_regex"} declares a tool search over tools marked defer_loading: true.
reasoningobject
Reasoning controls, translated for each provider.
Show 4 child fields
- effortstring
  How hard the model thinks. An effort the model does not take becomes the nearest one it does, named in x-sgr-ignored-parameters.
- max_tokensinteger
  A reasoning budget in tokens.
- enabledboolean
  Turn reasoning on or off.
- excludeboolean
  Keep the reasoning text out of the answer while the model still reasons.
providerobject
Steers one request across the model's providers. With the OpenAI SDK, send it in extra_body. Every field accepts null. A name matches a provider's display name, its tag or the tag's first part, ignoring case: llm.buzz or llm-buzz names llm.buzz's own provider, and llm-buzz/eu only its capacity in the EU.
Show 7 child fields
- orderstring[]
  Try these providers first, in this order, then the others. At most 64 names.
- onlystring[]
  Use only these providers.
- ignorestring[]
  Never use these providers.
- allow_fallbacksboolean
  false stops moving to other providers.
- sortstring
  The order to try providers in. Ignored when order is set.
  
  pricethroughputlatencysmart
- zdrboolean
  true keeps the request on providers that declare 0 days of retention.
- data_collectionstring
  deny keeps the request on providers that declare no training and 0 days of retention.
  
  allowdeny
session_idstring
A name for the conversation, 1 to 256 characters, so its turns stay on the provider that holds its cache.

Response 200

Anthropic's message object. usage always carries cache_creation_input_tokens and cache_read_input_tokens, and cost in US dollars; readable reasoning arrives as a thinking block.

Errors

400
A field is missing or malformed, or the model cannot do what the request asks, in Anthropic's error body as an invalid_request_error; the message names the field.
401
Messages keeps Anthropic's error body: a 401 is an authentication_error, a 402 a billing_error, a 403 a permission_error and a 429 a rate_limit_error.

Every error code