How do I use Claude Opus 5.5 through YepAPI?

Sign up for a free API key, then send requests to the /v1/ai/chat endpoint.

AnthropicText Generation/v1/ai/chatReasoning

Claude Opus 5.5

Access Claude Opus 5.5 through one API key. Anthropic Flagship for Reasoning & Coding.

Claude Opus 5.5 is Anthropic's flagship model for demanding reasoning, coding and long-horizon agentic work, succeeding Claude Opus 5. Opus 5.5 is the everyday flagship: coding agents on real repositories, review and bug finding, long-document reasoning, with Fable 5.1 reserved for the very hardest runs.

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2,400+

Developers

1.2M+

API calls served

100+

Endpoints

$0.01

Per call

Yep, that's it.

Try it live

Send a message and see Claude Opus 5.5 respond in real time.

POST/v1/ai/chatanthropic/claude-opus-5.5

Message *

Max Tokens

Maximum tokens in the response.

Stream

Real-time tokens

Hit "Send Request" to see the response

Context Window

1M tokens

Max Output

128K tokens

Input Price

$5.91 / 1M tokens

Output Price

$29.54 / 1M tokens

Strengths

✓

Newest Opus, cheaper than Opus 5

Succeeds Opus 5 with better coding and reasoning at a lower price: $5.91 / $29.54 versus $7.38 / $36.92 per 1M tokens.

✓

Large-codebase changes

Particularly strong at multi-step edits across big repositories and at reviewing other models' code.

✓

1M token context, 128K output

Handles up to 1,000,000 input tokens and returns up to 128,000 output tokens per call.

✓

Tools, vision and structured output

Function calling, image and file input, and JSON schema outputs.

Quick start

Copy this snippet and start making calls with Claude Opus 5.5.

const res = await fetch('https://api.yepapi.com/v1/ai/chat', {
  method: 'POST',
  headers: {
    'x-api-key': 'YOUR_API_KEY',
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    "model": "anthropic/claude-opus-5.5",
    "messages": [
      {
        "role": "user",
        "content": "Explain API gateways in 2 sentences."
      }
    ],
    "maxTokens": 256
  }),
});
const { data } = await res.json();
console.log(data.message.content);

Why use Claude Opus 5.5 through YepAPI?

✓One API key for all models — no separate accounts

✓OpenAI SDK compatible — just change the base URL

✓No monthly minimums — pay per token

✓Switch models with one line of code

✓Full provider passthrough — citations, search results, and all extras included

✓Streaming and non-streaming support on every model

✓Works with Cursor, Claude, LangChain, and any LLM tool

✓Unified billing across all providers

Claude Opus 5.5 API — pricing, context window & access

Claude Opus 5.5 is Anthropic's flagship model for demanding reasoning, coding and long-horizon agentic work, succeeding Claude Opus 5. It pairs a 1,000,000-token context window with up to 128,000 output tokens per response, at $5.91 per 1M input and $29.54 per 1M output tokens through YepAPI.

Through YepAPI you call Claude Opus 5.5 on an OpenAI-compatible endpoint with a single key — the same key that reaches GPT-6, Claude, Gemini, Grok and the SEO, SERP and scraping APIs. Input: text, images, files.

What is Claude Opus 5.5?

Claude Opus 5.5 is Anthropic's flagship model for demanding reasoning, coding and long-horizon agentic work, succeeding Claude Opus 5. It is particularly strong at multi-step changes in large codebases, code review, and analysis over long documents, and it is priced below Opus 5 at $5.91 / $29.54 per 1M tokens, with a 1,000,000-token context window and 128,000 output tokens. It accepts text, images, files as input, handles up to 1,000,000 tokens of context and returns up to 128,000 output tokens per call.

Build with Claude Opus 5.5 via YepAPI

YepAPI serves Claude Opus 5.5 on the OpenAI-compatible /v1/ai/chat endpoint. Point your base URL at YepAPI, add your key, and set the model string to claude-opus-5.5 (or the full anthropic/claude-opus-5.5). Function calling, structured outputs and reasoning settings pass straight through, and switching to any other model on the platform is a one-string change per request.

Claude Opus 5.5 API pricing — $5.91 / 1M input, $29.54 / 1M output

Claude Opus 5.5 costs $5.91 per 1M input tokens and $29.54 per 1M output tokens through YepAPI, pay per token with no minimums. Failed calls are never charged, and every request is itemised in your dashboard API Logs so you can see exactly what a 128,000-token response cost.

Claude Opus 5.5 use cases

Opus 5.5 is the everyday flagship: coding agents on real repositories, review and bug finding, long-document reasoning, with Fable 5.1 reserved for the very hardest runs.

Try Claude Opus 5.5 free

Every new YepAPI account includes $5 in free credit with no card required — enough to test Claude Opus 5.5 on your own prompts before committing to paid usage. Create an account, copy your key, and call claude-opus-5.5 right away.

Start generating in 30 seconds

$5 free credit on signup. No credit card required. Pay per call.

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What developers say

“Switched from SerpAPI and cut our SERP costs by 80%. Same data quality, way simpler billing.”
Marcus T.
SEO Platform Founder

“One API key for AI models, SERP data, and web scraping. Saved us from managing 4 separate providers.”
Priya S.
Full-Stack Developer

“The $5 free credit let us prototype our entire rank tracking feature before committing. No other API does that.”
Jake R.
Indie Hacker

Frequently asked questions

Input tokens cost $5.91 per 1M tokens and output tokens cost $29.54 per 1M tokens through YepAPI. No monthly minimums — you only pay for what you use.

Claude Opus 5.5 supports a 1M token context window with up to 128K output tokens per request.