Anthropic Claude (Sonnet 4.5 / Opus 4.5)

LLM

by Anthropic

Anthropic's Claude model family excels in nuanced reasoning, safety, and long-context tasks. Claude Sonnet 4.5 offers the best balance of cost and performance, while Opus 4.5 delivers frontier intelligence.

Official API Documentation$5 in free

API Endpoint

https://console.anthropic.com/

Documentation

Official Docs

Pricing

View Pricing

Registration & API Key Steps

Step 1

Visit console.anthropic.com and click "Sign up".

Open link

Step 2

Step 3

Complete phone verification to claim $5 free credits (US phone numbers recommended).

Step 4

Navigate to API Keys and create a new key.

Open link

Step 5

Copy and store your API key securely.

Step 6

Set up billing to increase your rate limits and spend caps.

Pricing

Tier	Price	Features
Claude Haiku 4.5	$1.00 / $5.00 per 1M tokens	Input / Output. Fast and affordable for simple tasks.
Claude Sonnet 4.5	$3.00 / $15.00 per 1M tokens	Input / Output. Best balance of intelligence and speed. Long-context (>200K): $6/$22.50.
Claude Opus 4.5	$5.00 / $25.00 per 1M tokens	Input / Output. Most capable model for complex tasks.
Claude Opus 4.6	$5.00 / $25.00 per 1M tokens	Input / Output. Latest flagship model with enhanced reasoning.
Batch API	50% off all models	Process within 24 hours. Sonnet 4.5: $1.50/$7.50 per 1M tokens.

Application Tips

Tip 1

Claude Sonnet 4.5 offers the best price-performance ratio for most use cases.

Tip 2

Use prompt caching (cache read tokens cost 10% of input price) for repeated system prompts.

Tip 3

Batch API provides 50% discount for non-urgent processing.

Tip 4

Tier system: Tier 1 ($5 deposit), Tier 2 ($40), Tier 3 ($200), Tier 4 ($400+).

Tip 5

Claude excels at nuanced writing, code review, and safety-sensitive applications.

Tip 6

Apply for Anthropic's startup program for $500+ in free credits.

China Access Solutions

Access Solution

Requires VPN/proxy. Chinese phone numbers not supported for registration. Consider third-party API relay services or Amazon Bedrock (available in some Asia-Pacific regions).

Code Example

JavaScript / TypeScript

import anthropic

client = anthropic.Anthropic(api_key="sk-ant-xxx")

message = client.messages.create(
    model="claude-sonnet-4-5-20250929",
    max_tokens=1024,
    messages=[
        {"role": "user", "content": "Explain the theory of relativity simply."}
    ]
)

print(message.content[0].text)

# --- cURL example ---
# curl https://api.anthropic.com/v1/messages \
#   -H "x-api-key: sk-ant-xxx" \
#   -H "anthropic-version: 2023-06-01" \
#   -H "content-type: application/json" \
#   -d '{
#     "model": "claude-sonnet-4-5-20250929",
#     "max_tokens": 1024,
#     "messages": [{"role": "user", "content": "Hello!"}]
#   }'

Rate Limits

Tier	Limits
Default	Tier 1: Sonnet 4.5 — 50 RPM, 40K ITPM, 8K OTPM. Tier 4: 4,000 RPM, 400K ITPM, 80K OTPM. Uses token bucket algorithm for smooth capacity.

Recommended Use Cases

Long document analysisCode generation & debuggingSafety-critical applicationsResearch & writingComplex reasoning

Last Updated: 2026-02-10

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