Fyoulink API Documentation

01Overview & Advantages

Fyoulink API is an independently operated third-party AI model API relay / acceleration service that gives developers stable, convenient access to the Claude model family.

• Dual-format compatibility: Supports both the native Anthropic format (/v1/messages) and the OpenAI-compatible format (/v1/chat/completions), so you can migrate with almost no changes to existing code.
• Works out of the box: Compatible with Claude Code, the official Anthropic SDK, the OpenAI SDK, and cURL — just swap the base URL and key.
• Transparent pricing: Top up at 1 RMB = 1 USD of credit, with a 1:1 model rate matching official pricing, billed by actual token usage.
• Extended context: Supports up to 1M (1,000,000) tokens of extended context (requires the corresponding beta header).
• Chinese-friendly: Built for Chinese-speaking developers — docs, examples, and support are all in Simplified Chinese.

02Quickstart (5-Minute Setup)

The whole process takes just four steps: create an account → verify your email → create an API key → top up → start calling the API.

03Base URL & Authentication

API Base URL

Authentication

Every request must include your API key (starting with sk-). Two delivery methods are supported — choose either one:

• Anthropic style: header x-api-key: sk-your-key
• Bearer style: header Authorization: Bearer sk-your-key

04Configuring Claude Code

Connecting Claude Code only requires setting two environment variables: ANTHROPIC_BASE_URL and ANTHROPIC_AUTH_TOKEN.

Method A: Environment Variables (Quick Test)

export ANTHROPIC_BASE_URL="https://www.fyoulink.com"
export ANTHROPIC_AUTH_TOKEN="sk-your-key"

claude

$env:ANTHROPIC_BASE_URL = "https://www.fyoulink.com"
$env:ANTHROPIC_AUTH_TOKEN = "sk-your-key"

claude

Method B: settings.json (Persistent, Recommended)

Create or edit settings.json inside the .claude directory in your home directory (Windows path %userprofile%\.claude; macOS / Linux path ~/.claude; if the directory doesn't exist, run claude once first to generate it automatically):

{
  "env": {
    "ANTHROPIC_BASE_URL": "https://www.fyoulink.com",
    "ANTHROPIC_AUTH_TOKEN": "sk-your-key"
  }
}

05Usage Examples (Copy & Run)

The examples below run as-is once you swap in your key. They default to the claude-sonnet-5 model — see Section 6 to switch to a different one.

Official Anthropic SDK (Python)

from anthropic import Anthropic

client = Anthropic(
    base_url="https://www.fyoulink.com",
    api_key="sk-your-key",
)

resp = client.messages.create(
    model="claude-sonnet-5",
    max_tokens=1024,
    messages=[{"role": "user", "content": "Introduce Fyoulink API in one sentence."}],
)
print(resp.content[0].text)

OpenAI-Compatible SDK (Python)

from openai import OpenAI

client = OpenAI(
    base_url="https://www.fyoulink.com/v1",
    api_key="sk-your-key",
)

resp = client.chat.completions.create(
    model="claude-sonnet-5",
    messages=[{"role": "user", "content": "Introduce Fyoulink API in one sentence."}],
)
print(resp.choices[0].message.content)

cURL — Anthropic Native Format

curl https://www.fyoulink.com/v1/messages \
  -H "x-api-key: sk-your-key" \
  -H "anthropic-version: 2023-06-01" \
  -H "content-type: application/json" \
  -d '{"model":"claude-sonnet-5","max_tokens":1024,
       "messages":[{"role":"user","content":"Hello, Fyoulink!"}]}'

cURL — OpenAI-Compatible Format

curl https://www.fyoulink.com/v1/chat/completions \
  -H "Authorization: Bearer sk-your-key" \
  -H "content-type: application/json" \
  -d '{"model":"claude-sonnet-5",
       "messages":[{"role":"user","content":"Hello, Fyoulink!"}]}'

06Supported Models

Fyoulink supports the full Claude model family. The table below lists commonly used models — the live list shown in the dashboard is authoritative (updated as new models ship). Prices are in USD per million tokens.

07Billing & Top-up

• Exchange rate: Top up at 1 RMB = 1 USD of credit.
• Model rate: 1:1, matching official model pricing with no markup.
• Billing method: Billed by actual token usage — cost = input tokens + output tokens, charged at the price of the model used.
• Balance rules: Credit is deducted in real time on each call; calls are paused once the balance runs out and resume automatically after you top up.

08Extended Context (1M)

Fyoulink supports up to 1M (1,000,000) tokens of extended context, ideal for very large codebases, long-document analysis, and similar scenarios. Your request must include the corresponding beta header (refer to the latest identifier announced on the official site).

curl https://www.fyoulink.com/v1/messages \
  -H "x-api-key: sk-your-key" \
  -H "anthropic-version: 2023-06-01" \
  -H "anthropic-beta: context-1m-2025-08-07" \
  -H "content-type: application/json" \
  -d '{"model":"claude-sonnet-5","max_tokens":2048, ...}'

09Concurrency & Rate Limits

• Default concurrency: Each account defaults to 5 concurrent requests.
• How to adjust: Upgrade based on your plan, or contact support at email@fyoulink.com to request a change.
• If you exceed the concurrency limit or trigger rate limiting, the API may return 429 Too Many Requests. We recommend implementing exponential backoff retries on the client side (start with a 1s wait, doubling each time).

10Frequently Asked Questions

11Contact & Support

• Technical support email: email@fyoulink.com (placeholder address — replace with the actual one)
• Official site: https://www.fyoulink.com
• When reporting an issue, please include: the model used, a sample request (be sure to redact the full key), the error code, and the timestamp, so we can resolve it quickly.