Anthropic: Claude Opus 4

anthropic/claude-opus-4

Claude Opus 4 is benchmarked as the world’s best coding model, at time of release, bringing sustained performance on complex, long-running tasks and agent workflows. It sets new benchmarks in software...

visiontools

MODALITIES

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INPUT PRICE

$15per 1M

OUTPUT PRICE

$75per 1M

CONTEXT

200K

RELEASED

May 23, 2025

Provider				Cache	Uptime	Chat
FastAPI	—	$15	$75	Cache read$1.5

Capabilities

Input modalities

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Output modalities

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Features

include_reasoningmax_tokensreasoningstoptemperaturetool_choicetoolstop_p

Get your API key

Create an API key from the Keys page, then set it as an environment variable:

export ONLIST_API_KEY=sk-...

Make your first request

Endpoints

POSThttps://onlist.io/v1/chat/completions

OpenAI Chat Completions format

Request Headers

Authorization:Bearer $ONLIST_API_KEY

Content-Type:application/json

Model:anthropic/claude-opus-4

POSThttps://onlist.io/v1/responses

OpenAI Responses format

Request Headers

Authorization:Bearer $ONLIST_API_KEY

Content-Type:application/json

Model:anthropic/claude-opus-4

POSThttps://onlist.io/v1/messages

Anthropic Messages format

Request Headers

Authorization:Bearer $ONLIST_API_KEY

Content-Type:application/json

Model:anthropic/claude-opus-4

Code samples

curl https://onlist.io/v1/chat/completions \
  -H "Authorization: Bearer $ONLIST_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
       "model": "anthropic/claude-opus-4",
       "messages": [
         {
           "role": "user",
           "content": "Explain quantum entanglement in one paragraph."
         }
       ]
     }'

Replace $ONLIST_API_KEY with the API key from your Keys page.

Authentication

All requests must include an Authorization: Bearer <TOKEN> header. Generate keys from the Keys page; keys can be scoped to specific models, groups, IP ranges, and rate limits.

Enable streaming

Add "stream": true to receive partial responses as server-sent events in real time.

Streaming example

curl https://onlist.io/v1/chat/completions \
  -H "Authorization: Bearer $ONLIST_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
       "model": "anthropic/claude-opus-4",
       "messages": [
         {
           "role": "user",
           "content": "Write a haiku about recursion."
         }
       ],
       "stream": true
     }'

Supported parameters

Name	Type	Description
`include_reasoning`
`max_tokens`	integer	Maximum number of tokens to generate in the completion.
`reasoning`
`stop`	string \| array	Up to 4 sequences where the API will stop generating tokens.
`temperature`	number	Sampling temperature between 0 and 2. Higher values make output more random.
`tool_choice`	string \| object	Controls which tool is called. "auto", "none", "required", or a specific function.
`tools`	array	A list of tools the model may call. Currently supports functions.
`top_p`	number	Nucleus sampling. The model considers tokens with top_p probability mass.

These are the request parameters this model accepts. Parameter semantics follow the OpenAI Chat Completions specification.