Anthropic Format Overview

What is Anthropic Native Format?

Samurai AI supports two API formats side-by-side:

Format	Endpoint	Auth Header	SDK
OpenAI-compatible	`POST /v1/chat/completions`	`Authorization: Bearer sk-...`	`openai`
Anthropic-native	`POST /v1/messages`	`x-api-key: sk-...`	`anthropic`

If you already use the official anthropic Python or TypeScript SDK — or call api.anthropic.com directly — you can switch to Samurai AI by changing one line: the base_url.

# Before (Anthropic Cloud)
from anthropic import Anthropic
client = Anthropic(api_key="sk-ant-...")

# After (Samurai AI — everything else stays the same)
from anthropic import Anthropic
client = Anthropic(
    base_url="https://www.samuraiapi.in/api",
    api_key="YOUR_SAMURAI_KEY"
)

Base URL for Anthropic format: https://www.samuraiapi.in/apiThe Anthropic SDK appends /v1/messages automatically. Do not include it in the base URL.

Supported Claude Models

Model ID	Context	Best For
`claude-opus-4-5`	200K	Complex analysis, research, long documents
`claude-sonnet-4-5`	200K	Balanced performance, most tasks
`claude-3-5-sonnet-20241022`	200K	Coding, reasoning, instruction-following
`claude-3-5-haiku-20241022`	200K	Fast, low-latency responses
`claude-3-opus-20240229`	200K	Deep reasoning, nuanced writing

You can also use Claude models through the OpenAI-compatible /v1/chat/completions endpoint — Samurai AI converts the format automatically. Use whichever endpoint matches your existing SDK.

Key Differences from OpenAI Format

1. System prompt is a top-level field

# OpenAI format — system message inside messages array
messages = [
    {"role": "system", "content": "You are a helpful assistant."},
    {"role": "user", "content": "Hello!"}
]

# Anthropic format — system is a separate top-level parameter
response = client.messages.create(
    model="claude-3-5-sonnet-20241022",
    max_tokens=1024,
    system="You are a helpful assistant.",   # <-- top-level
    messages=[
        {"role": "user", "content": "Hello!"}
    ]
)

2. `max_tokens` is required

The Anthropic API always requires max_tokens. There is no default.

3. Response is a `Message` object, not a `ChatCompletion`

// OpenAI response
{
  "object": "chat.completion",
  "choices": [{ "message": { "role": "assistant", "content": "..." } }]
}

// Anthropic response
{
  "type": "message",
  "role": "assistant",
  "content": [{ "type": "text", "text": "..." }]
}

4. Tool definitions use `input_schema` instead of `parameters`

# OpenAI format
tools = [{"type": "function", "function": {"name": "get_weather", "parameters": {...}}}]

# Anthropic format
tools = [{"name": "get_weather", "input_schema": {...}}]

5. Auth header is `x-api-key`

# OpenAI
-H "Authorization: Bearer sk-samurai-..."

# Anthropic
-H "x-api-key: sk-samurai-..."
-H "anthropic-version: 2023-06-01"

Quick Start

from anthropic import Anthropic

client = Anthropic(
    base_url="https://www.samuraiapi.in/api",
    api_key="YOUR_SAMURAI_KEY"
)

message = client.messages.create(
    model="claude-3-5-sonnet-20241022",
    max_tokens=1024,
    system="You are a helpful assistant.",
    messages=[
        {"role": "user", "content": "Explain the theory of relativity in simple terms."}
    ]
)

print(message.content[0].text)
print(f"Used {message.usage.input_tokens} input + {message.usage.output_tokens} output tokens")

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

const client = new Anthropic({
  baseURL: "https://www.samuraiapi.in/api",
  apiKey: process.env.SAMURAI_API_KEY!,
});

const message = await client.messages.create({
  model: "claude-3-5-sonnet-20241022",
  max_tokens: 1024,
  system: "You are a helpful assistant.",
  messages: [
    { role: "user", content: "Explain the theory of relativity in simple terms." }
  ],
});

console.log(message.content[0].type === "text" ? message.content[0].text : "");

curl https://www.samuraiapi.in/api/v1/messages \
  -H "x-api-key: YOUR_SAMURAI_KEY" \
  -H "anthropic-version: 2023-06-01" \
  -H "content-type: application/json" \
  -d '{
    "model": "claude-3-5-sonnet-20241022",
    "max_tokens": 1024,
    "system": "You are a helpful assistant.",
    "messages": [
      {"role": "user", "content": "Explain the theory of relativity in simple terms."}
    ]
  }'

SDK Installation

pip install anthropic

npm install @anthropic-ai/sdk

Authentication

Use your Samurai AI API key in the x-api-key header. The same key works for both OpenAI-compatible and Anthropic-native endpoints.

# Get your key from: https://www.samuraiapi.in/dashboard
x-api-key: sk-samurai-YOUR_KEY_HERE

The anthropic-version: 2023-06-01 header is required by the official SDK — Samurai AI accepts it and forwards it as needed.

Rate Limits & Quotas

Anthropic-format requests use the same quotas and rate limits as OpenAI-format requests. Your plan limits apply across both endpoints.

Plan	Requests/min	Notes
Free	10 RPM	Shared across all endpoints
Starter	60 RPM	—
Pro	200 RPM	—
Enterprise	Custom	Contact us

Next Steps

Messages API

Full reference for the /v1/messages endpoint — parameters, streaming, tool use, vision.

Function Calling

Tool use with the OpenAI-compatible format (also works with Claude models).

Overview

Getting Started

Chat & Text