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How to Use the Claude Opus 4.6 API: A Step-by-Step Tutorial

Recently, Anthropic launched its most powerful model to date — Claude Opus 4.6. It sets new benchmarks in coding, AI Agents, and enterprise workflows, boasting a massive 1M context window and powerful hybrid reasoning capabilities. For developers, this means the ability to build smarter, more reliable AI applications.

How to Use the Claude Opus 4.6 API

To unleash the full potential of Claude Opus 4.6, the first step is to learn how to call its API. Writing code directly for debugging can be both time-consuming and tedious, especially for developers who are new to APIs. A more efficient way is to use a professional API tool that allows you to intuitively build and test API requests in a graphical interface. Apidog is such a powerful tool that integrates API design, debugging, and testing, making it perfect for exploring and debugging the Claude API.

This article will detail how to use Apidog to call the Claude Opus 4.6 API step-by-step from scratch, allowing you to interact intuitively with this top-tier AI model without writing any code.

Preparation: Get Your API Key

Before communicating with any API, you need a credential to prove you have access rights, typically called an API Key. It is a unique string that needs to be attached to every request so the server can verify your identity.

To get a Claude API Key, you need to visit Anthropic's official Claude Developer Platform. After logging into your account, you can usually find the option to create a new key in your account settings or on a dedicated "API Keys" page.

Once generated, the system will provide a string starting with sk-. This is your API Key, please keep it secure. It acts as the password for accessing Claude services, and anyone with this Key can use your account quota. We will use this Key in subsequent steps.

Understanding Claude Messages Endpoint

Claude provides an API called the Messages Endpoint, specifically designed to handle conversations with the model. When calling this API, we need to clarify several core elements:

  • Endpoint URL: This is the "mailing address" of the API. For the Claude Messages API, the address is https://api.anthropic.com/v1/messages.

  • HTTP Method: This is the "sending method". To send instructions to Claude and get a response, we need to use the POST method because it involves submitting data (our question) to the server.

  • Headers: These are the "envelope headers" containing important metadata, such as our identity credential (API Key) and content format specifications.

  • Request Body: This is the "letter content" containing the specific task we want the model to perform, such as the question to ask or the specified model.

For the Claude API, several key Headers are crucial, as shown in the table below:

Header

Example Value

Description

x-api-key

sk-xxxxxxxxxxxxxxxxx

The API Key for authentication. Replace with your own Key.

anthropic-version

2023-06-01

Specifies the API version you wish to use, ensuring your request isn't broken by API updates.

Content-Type

application/json

Tells the server that the request body we are sending is in JSON format.

With these basic concepts understood, we can start building our first request in Apidog.

Sending Your First Request with Apidog

Apidog provides a clean graphical interface that allows us to configure API requests just like filling out a form, which is very intuitive.

Step 1: Create a New Project and Request

Open the Apidog client, where you can create a new project to manage your Claude API. In the project, click the "+" button on the left, select "HTTP Endpoint", and create a new HTTP request. You can name this request "Claude Chat" for easy lookup later.

Try it

How to Use the Claude Opus 4.6 API

Step 2: Quick Import using cURL Command

In actual work, we often see cURL commands in API documentation or examples. cURL is a powerful command-line tool for sending network requests. Apidog provides a very convenient feature: directly parsing cURL commands.

A complete cURL command to call the Claude API might look like this. Note that you need to replace YOUR_API_KEY with your actual API Key.

curl https://api.anthropic.com/v1/messages \
     --header "x-api-key: YOUR_API_KEY" \
     --header "anthropic-version: 2023-06-01" \
     --header "Content-Type: application/json" \
     --data '{
         "model": "claude-opus-4-6",
         "max_tokens": 1024,
         "messages": [
             {"role": "user", "content": "Hello, please introduce yourself."}
         ]
     }'
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In Apidog, there is no need to manually dismantle this command. Simply copy the entire cURL command above and paste it directly into Apidog's url bar.

How to Use the Claude Opus 4.6 API

Apidog will intelligently identify it as a cURL command and automatically fill in the request method, URL, Headers, and Body for you. This feature greatly improves debugging efficiency, especially when dealing with APIs containing many parameters and complex request bodies.

Step 3: Manually Construct the Request (Optional)

If you don't want to use cURL for quick import, you can also manually construct a request.

First, configure the request method and URL. According to Anthropic's API specifications, creating a conversation typically uses the POST method. Its official API base URL is https://api.anthropic.com, and the specific conversation endpoint path is /v1/messages.

So, in Apidog's url bar, select the POST method and enter the complete URL: https://api.anthropic.com/v1/messages.

Next, configure the request headers (Headers). The API server uses headers to obtain metadata, such as authentication info and content format. Calling the Claude API requires the following Headers:

  • x-api-key: Used to store your API Key.

  • anthropic-version: Specifies the API version number; this is a required field. According to official docs, you can enter a date here, e.g., 2023-06-01.

  • Content-Type: Declares the data format of the request body. Since we are sending JSON data, the value should be application/json.

In Apidog's "Headers" tab, add these three items one by one.

After configuring headers, the most important part is building the request body (Body). The body carries the specific task we want Claude to perform. Switch to the "Body" tab, select JSON format, and enter the following content:

{
  "model": "claude-opus-4-6",
  "max_tokens": 1024,
  "messages": [
    {
      "role": "user",
      "content": "Hello, please introduce yourself."
    }
  ]
}
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This JSON data contains three key fields:

  • model: Specifies the model name to call; here we use claude-opus-4-6.

  • max_tokens: Sets the maximum length of content generated by the model (in Tokens).

  • messages: An array containing conversation history. Each object represents a message, where role indicates the role (user for the user) and content is the specific message content.

Step 4: Send Request and View Response

After completing any of the above steps, save the interface and go to the "Request" debugging page. If the API Key hasn't been replaced, you need to replace YOUR_API_KEY in the Headers with your actual API Key.

How to Use the Claude Opus 4.6 API

Then, click the "Send" button on the Apidog interface. If everything is normal, you will see the result returned by Claude Opus 4.6 in the "Response" area below after a short wait.

How to Use the Claude Opus 4.6 API

Apidog will send our constructed request to Anthropic's servers. Moments later, we can see the result returned by Claude in the "Response" area. A successful response is usually also in JSON format, containing the answer generated by the model.

{
  "model": "claude-opus-4-6",
  "id": "msg_01...",
  "type": "message",
  "role": "assistant",
  "content": [
    {
      "type": "text",
      "text": "Hello! I am Claude ..........."
    }
  ],
  ...
}
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As you can see, the text field within the returned content array contains the answer from Claude Opus 4.6. This marks the successful completion of our first API call.

Exploring More Rich API Parameters

After mastering the basic calling method, we can further explore other parameters provided by the Messages API to achieve more complex interactions and finer control.

Streaming

By default, the API returns the complete response at once after the model finishes generating all content. For longer answers, users might have to wait a while. Streaming solves this problem by allowing the server to return content character by character or word by word, creating a typewriter-like real-time effect.

To enable streaming, simply add a field "stream": true to the JSON request body.

{
  "model": "claude-opus-4-6",
  "max_tokens": 1024,
  "messages": [
    {
      "role": "user",
      "content": "Hello, please introduce yourself."
    }
  ],
  "stream": true
}
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When this request is sent, Apidog's response area will continuously receive the data stream in the form of Server-Sent Events (SSE), displaying the content generated by the model in real-time, which is very useful for building interactive chat applications.

How to Use the Claude Opus 4.6 API

Controlling Creativity and Randomness

temperature is a very interesting parameter that controls the randomness of the model's output. Its value typically ranges between 0.0 and 1.0.

  • A lower temperature (e.g., 0.2) makes the model's answers more deterministic and consistent, suitable for scenarios requiring precise, objective answers like factual Q&A or code generation.

  • A higher temperature (e.g., 0.8) makes the model's answers more creative and diverse, suitable for scenarios like brainstorming and creative writing.

Add the temperature field in the JSON to adjust it:

{
  "model": "claude-opus-4-6",
  "max_tokens": 1024,
  "temperature": 0.7,
  "messages": [
    {
      "role": "user",
      "content": "Give me an idea for a sci-fi novel."
    }
  ]
}
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Multi-turn Conversation

Real conversation is not a one-off Q&A but a continuous exchange with context. The design of the Messages API naturally supports multi-turn conversations. The implementation is very simple: just include the entire previous conversation history in the messages array.

For example, after asking the first question and getting an answer, we can build a second request that includes the Q&A from the first round:

{
  "model": "claude-opus-4-6",
  "max_tokens": 1024,
  "messages": [
    {
      "role": "user",
      "content": "What is the capital of France?"
    },
    {
      "role": "assistant",
      "content": "The capital of France is Paris."
    },
    {
      "role": "user",
      "content": "What are the famous attractions there?"
    }
  ]
}
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In this request, we included the user's first question, the model's first answer, and the user's second question. This way, when answering "What are the famous attractions there?", the model can understand that "there" refers to "Paris" and provide relevant answers.

To facilitate review, the following table summarizes the functions of several common API parameters:

Parameter

Type

Description

model

string

Specifies the model to use, e.g., claude-opus-4-6.

messages

array

Conversation history, containing alternating messages from user and assistant.

max_tokens

integer

Limit on the maximum length of generated content.

temperature

float

Controls output randomness; higher values are more creative.

stream

boolean

Whether to enable streaming; true means enabled.

Using Apidog to Boost Debugging Efficiency

Apidog is not just a request sending tool; it also provides many advanced features that can significantly improve the efficiency of API debugging and development.

Manage API Keys with Environment Variables

Hardcoding API Keys directly in request headers poses security risks and makes it inconvenient to switch between different environments (like development and production). Apidog's environment variable feature can solve this problem perfectly.

We can create a variable named claude_api_key in Apidog's environment management and set its value to your API Key.

How to Use the Claude Opus 4.6 API

Then, in the Headers settings of the request, modify the value of x-api-key to {{claude_api_key}}.

How to Use the Claude Opus 4.6 API

This way, Apidog will automatically replace it with the real value when sending the request. When you need to change the Key, just modify the environment variable, and all endpoints using this variable will automatically update—safe and efficient.

Save and Reuse Endpoints

Endpoint debugging in Apidog can be saved. This means your constructed Claude API requests, including URL, Headers, Body, and various parameter configurations, can be reused with one click. This is not only convenient for your own repeated testing but also facilitates sharing with team members to ensure everyone uses a unified API definition for collaborative development.

Auto-generate Code

One of the most exciting features after successfully debugging an API in Apidog is "Code Generation". You can find a "Generate Code" option on the right side of the endpoint documentation.

How to Use the Claude Opus 4.6 API

After clicking, Apidog can automatically generate code in multiple programming languages and frameworks based on your current request configuration, such as Python (requests library), JavaScript (axios or fetch), Java, Go, Curl, etc.

How to Use the Claude Opus 4.6 API

This means seamless integration from API debugging to the project. You don't need to manually write tedious HTTP request code; just copy the code snippet generated by Apidog into your project to quickly implement the call to the Claude API, allowing you to focus entirely on developing business logic.

Through the above steps, we have not only learned how to use Apidog to call and debug the Claude Opus 4.6 API but also mastered methods to use advanced features to improve development efficiency. From sending the first "Hello" to implementing multi-turn conversations with context, and then to one-click project code generation, the entire process is completed in an intuitive, unified platform. This paves the way for you to further explore Claude's powerful capabilities and build innovative AI applications.

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