---
title: Using the Messages API
url: https://platform.claude.com/docs/en/build-with-claude/working-with-messages
description: Practical patterns and examples for using the Messages API effectively
---

Anthropic offers two ways to build with Claude, each suited to different use cases:

|                | Messages API                                | Claude Managed Agents                                                     |
| -------------- | ------------------------------------------- | ------------------------------------------------------------------------- |
| **What it is** | Direct model prompting access               | Pre-built, configurable agent harness that runs in managed infrastructure |
| **Best for**   | Custom agent loops and fine-grained control | Long-running tasks and asynchronous work                                  |

This guide covers common patterns for working with the Messages API, including basic requests, multi-turn conversations, prefill techniques, and vision capabilities. For complete API specifications, see the [Messages API reference](https://platform.claude.com/docs/en/api/messages/create). For the managed agent harness instead, see the [Claude Managed Agents overview](https://platform.claude.com/docs/en/managed-agents/overview).

<Note>
  To learn how zero data retention (ZDR) applies to this feature, see [API and data retention](https://platform.claude.com/docs/en/manage-claude/api-and-data-retention).
</Note>

## Basic request and response

<Note>
  The `temperature`, `top_p`, and `top_k` sampling parameters are not supported on Claude 4.7 and later models and Claude Mythos Preview. Setting them to a non-default value returns a 400 error. Omit them from request payloads and use prompting to guide the model's behavior instead. See the [migration guide](https://platform.claude.com/docs/en/models/opus-5-5/migration-guide#opus-46-breaking-changes).
</Note>

<CodeGroup>
  ```bash cURL
  #!/bin/sh
  curl https://api.anthropic.com/v1/messages \
    -H "x-api-key: $ANTHROPIC_API_KEY" \
    -H "anthropic-version: 2023-06-01" \
    -H "content-type: application/json" \
    -d '{
      "model": "claude-opus-5-5",
      "max_tokens": 1024,
      "messages": [
        {"role": "user", "content": "Hello, Claude"}
      ]
    }'
  ```

  ```bash CLI
  ant messages create \
    --model claude-opus-5-5 \
    --max-tokens 1024 \
    --message '{role: user, content: "Hello, Claude"}'
  ```

  ```python Python
  message = anthropic.Anthropic().messages.create(
      model="claude-opus-5-5",
      max_tokens=1024,
      messages=[{"role": "user", "content": "Hello, Claude"}],
  )
  print(message)
  ```

  ```typescript TypeScript
  const anthropic = new Anthropic();

  const message = await anthropic.messages.create({
    model: "claude-opus-5-5",
    max_tokens: 1024,
    messages: [{ role: "user", content: "Hello, Claude" }]
  });
  console.log(message);
  ```

  ```csharp C#
  AnthropicClient client = new();

  var parameters = new MessageCreateParams
  {
      Model = Model.ClaudeOpus5_5,
      MaxTokens = 1024,
      Messages = [new() { Role = Role.User, Content = "Hello, Claude" }]
  };
  var message = await client.Messages.Create(parameters);
  Console.WriteLine(message);
  ```

  ```go Go
  client := anthropic.NewClient()

  response, err := client.Messages.New(context.TODO(), anthropic.MessageNewParams{
  	Model:     anthropic.ModelClaudeOpus5_5,
  	MaxTokens: 1024,
  	Messages: []anthropic.MessageParam{
  		anthropic.NewUserMessage(anthropic.NewTextBlock("Hello, Claude")),
  	},
  })
  if err != nil {
  	log.Fatal(err)
  }
  fmt.Println(response)
  ```

  ```java Java
  AnthropicClient client = AnthropicOkHttpClient.fromEnv();

  MessageCreateParams params = MessageCreateParams.builder()
      .model(Model.CLAUDE_OPUS_5_5)
      .maxTokens(1024L)
      .addUserMessage("Hello, Claude")
      .build();

  Message response = client.messages().create(params);
  System.out.println(response);
  ```

  ```php PHP
  $client = new Client();

  $message = $client->messages->create(
      maxTokens: 1024,
      messages: [['role' => 'user', 'content' => 'Hello, Claude']],
      model: 'claude-opus-5-5',
  );
  echo json_encode($message, JSON_PRETTY_PRINT), PHP_EOL;
  ```

  ```ruby Ruby
  client = Anthropic::Client.new

  message = client.messages.create(
    model: "claude-opus-5-5",
    max_tokens: 1024,
    messages: [
      { role: "user", content: "Hello, Claude" }
    ]
  )
  puts message
  ```
</CodeGroup>

```json Output
{
  "id": "msg_01XFDUDYJgAACzvnptvVoYEL",
  "type": "message",
  "role": "assistant",
  "content": [
    {
      "type": "text",
      "text": "Hello!"
    }
  ],
  "model": "claude-opus-5-5",
  "stop_reason": "end_turn",
  "stop_sequence": null,
  "usage": {
    "input_tokens": 12,
    "output_tokens": 6
  }
}
```

Refusal responses (`stop_reason: "refusal"`) also include a `stop_details` object identifying the policy category that triggered the refusal, on every model. See [Handling stop reasons](https://platform.claude.com/docs/en/build-with-claude/refusals-and-fallback#refusal-response) for the field reference and example handling code.

## Multiple conversational turns

The Messages API is stateless, which means that you always send the full conversational history to the API. You can use this pattern to build up a conversation over time. Earlier conversational turns don't necessarily need to actually originate from Claude. You can use synthetic `assistant` messages.

<CodeGroup>
  ```bash cURL
  #!/bin/sh
  curl https://api.anthropic.com/v1/messages \
    -H "x-api-key: $ANTHROPIC_API_KEY" \
    -H "anthropic-version: 2023-06-01" \
    -H "content-type: application/json" \
    -d '{
      "model": "claude-opus-5-5",
      "max_tokens": 1024,
      "messages": [
        {"role": "user", "content": "Hello, Claude"},
        {"role": "assistant", "content": "Hello!"},
        {"role": "user", "content": "Can you describe LLMs to me?"}

      ]
    }'
  ```

  ```bash CLI
  ant messages create \
    --model claude-opus-5-5 \
    --max-tokens 1024 \
    --message '{role: user, content: "Hello, Claude"}' \
    --message '{role: assistant, content: "Hello!"}' \
    --message '{role: user, content: "Can you describe LLMs to me?"}'
  ```

  ```python Python
  message = anthropic.Anthropic().messages.create(
      model="claude-opus-5-5",
      max_tokens=1024,
      messages=[
          {"role": "user", "content": "Hello, Claude"},
          {"role": "assistant", "content": "Hello!"},
          {"role": "user", "content": "Can you describe LLMs to me?"},
      ],
  )
  print(message)
  ```

  ```typescript TypeScript
  const anthropic = new Anthropic();

  const message = await anthropic.messages.create({
    model: "claude-opus-5-5",
    max_tokens: 1024,
    messages: [
      { role: "user", content: "Hello, Claude" },
      { role: "assistant", content: "Hello!" },
      { role: "user", content: "Can you describe LLMs to me?" }
    ]
  });
  console.log(message);
  ```

  ```csharp C#
  AnthropicClient client = new();

  var parameters = new MessageCreateParams
  {
      Model = Model.ClaudeOpus5_5,
      MaxTokens = 1024,
      Messages =
      [
          new() { Role = Role.User, Content = "Hello, Claude" },
          new() { Role = Role.Assistant, Content = "Hello!" },
          new() { Role = Role.User, Content = "Can you describe LLMs to me?" }
      ]
  };

  var message = await client.Messages.Create(parameters);
  Console.WriteLine(message);
  ```

  ```go Go
  client := anthropic.NewClient()

  response, err := client.Messages.New(context.TODO(), anthropic.MessageNewParams{
  	Model:     anthropic.ModelClaudeOpus5_5,
  	MaxTokens: 1024,
  	Messages: []anthropic.MessageParam{
  		anthropic.NewUserMessage(anthropic.NewTextBlock("Hello, Claude")),
  		anthropic.NewAssistantMessage(anthropic.NewTextBlock("Hello!")),
  		anthropic.NewUserMessage(anthropic.NewTextBlock("Can you describe LLMs to me?")),
  	},
  })
  if err != nil {
  	log.Fatal(err)
  }
  fmt.Println(response)
  ```

  ```java Java
  AnthropicClient client = AnthropicOkHttpClient.fromEnv();

  MessageCreateParams params = MessageCreateParams.builder()
      .model(Model.CLAUDE_OPUS_5_5)
      .maxTokens(1024L)
      .addUserMessage("Hello, Claude")
      .addAssistantMessage("Hello!")
      .addUserMessage("Can you describe LLMs to me?")
      .build();

  Message response = client.messages().create(params);
  System.out.println(response);
  ```

  ```php PHP
  $client = new Client();

  $message = $client->messages->create(
      maxTokens: 1024,
      messages: [
          ['role' => 'user', 'content' => 'Hello, Claude'],
          ['role' => 'assistant', 'content' => 'Hello!'],
          ['role' => 'user', 'content' => 'Can you describe LLMs to me?'],
      ],
      model: 'claude-opus-5-5',
  );

  echo json_encode($message, JSON_PRETTY_PRINT), PHP_EOL;
  ```

  ```ruby Ruby
  client = Anthropic::Client.new

  message = client.messages.create(
    model: "claude-opus-5-5",
    max_tokens: 1024,
    messages: [
      { role: "user", content: "Hello, Claude" },
      { role: "assistant", content: "Hello!" },
      { role: "user", content: "Can you describe LLMs to me?" }
    ]
  )
  puts message
  ```
</CodeGroup>

```json Output
{
  "id": "msg_018gCsTGsXkYJVqYPxTgDHBU",
  "type": "message",
  "role": "assistant",
  "content": [
    {
      "type": "text",
      "text": "Sure, I'd be happy to provide..."
    }
  ],
  "model": "claude-opus-5-5",
  "stop_reason": "end_turn",
  "stop_sequence": null,
  "usage": {
    "input_tokens": 30,
    "output_tokens": 309
  }
}
```

### System role in messages

On Claude Fable 5.1, [Claude Mythos 5.1](https://platform.claude.com/docs/en/models/mythos-5-1/overview), Claude Fable 5, [Claude Mythos 5](https://platform.claude.com/docs/en/models/mythos-5/overview), Claude Opus 5.5, Claude Opus 4.8, Claude Opus 5, Claude Sonnet 5.5, and Claude Haiku 5.5, you can include messages with `"role": "system"` after a user turn (subject to [placement rules](https://platform.claude.com/docs/en/build-with-claude/mid-conversation-system-messages#limitations)) to add a new system instruction partway through a conversation. A `system` message that carries content cannot be the first entry in `messages`. Use the top-level `system` field for instructions that apply from the start.

A mid-conversation system message has the same authority as the top-level `system` field, but because it is appended to the end of the message history, it does not invalidate any cached prefix that came before it. Use the top-level `system` field for instructions that should apply from the very first turn, and a mid-conversation system message for instructions that only become relevant later.

See [Mid-conversation system messages](https://platform.claude.com/docs/en/build-with-claude/mid-conversation-system-messages) for the complete guide, including how to combine it with [prompt caching](https://platform.claude.com/docs/en/build-with-claude/prompt-caching).

## Prefilling Claude's response

You can pre-fill part of Claude's response in the last position of the input messages list. Use this technique to shape Claude's response. The following example uses `"max_tokens": 1` to get a single multiple choice answer from Claude.

<Warning>
  Prefilling is not supported on Claude 4.6 and later models and [Claude Mythos Preview](https://anthropic.com/glasswing). Requests using prefill with these models return a 400 error. Use [structured outputs](https://platform.claude.com/docs/en/build-with-claude/structured-outputs) on models that support it, or system prompt instructions, instead. See the [migration guide](https://platform.claude.com/docs/en/about-claude/models/migration-guide) for migration patterns.
</Warning>

<CodeGroup>
  ```bash cURL
  #!/bin/sh
  curl https://api.anthropic.com/v1/messages \
    -H "x-api-key: $ANTHROPIC_API_KEY" \
    -H "anthropic-version: 2023-06-01" \
    -H "content-type: application/json" \
    -d '{
      "model": "claude-sonnet-4-5",
      "max_tokens": 1,
      "messages": [
        {"role": "user", "content": "What is latin for Ant? (A) Apoidea, (B) Rhopalocera, (C) Formicidae"},
        {"role": "assistant", "content": "The answer is ("}
      ]
    }'
  ```

  ```bash CLI
  ant messages create <<'YAML'
  model: claude-sonnet-4-5
  max_tokens: 1
  messages:
    - role: user
      content: "What is latin for Ant? (A) Apoidea, (B) Rhopalocera, (C) Formicidae"
    - role: assistant
      content: "The answer is ("
  YAML
  ```

  ```python Python
  message = anthropic.Anthropic().messages.create(
      model="claude-sonnet-4-5",
      max_tokens=1,
      messages=[
          {
              "role": "user",
              "content": "What is latin for Ant? (A) Apoidea, (B) Rhopalocera, (C) Formicidae",
          },
          {"role": "assistant", "content": "The answer is ("},
      ],
  )
  print(message)
  ```

  ```typescript TypeScript
  const anthropic = new Anthropic();

  const message = await anthropic.messages.create({
    model: "claude-sonnet-4-5",
    max_tokens: 1,
    messages: [
      {
        role: "user",
        content: "What is latin for Ant? (A) Apoidea, (B) Rhopalocera, (C) Formicidae"
      },
      { role: "assistant", content: "The answer is (" }
    ]
  });
  console.log(message);
  ```

  ```csharp C#
  AnthropicClient client = new();

  var parameters = new MessageCreateParams
  {
      Model = Model.ClaudeSonnet4_5,
      MaxTokens = 1,
      Messages = [
          new() { Role = Role.User, Content = "What is latin for Ant? (A) Apoidea, (B) Rhopalocera, (C) Formicidae" },
          new() { Role = Role.Assistant, Content = "The answer is (" }
      ]
  };

  var message = await client.Messages.Create(parameters);
  Console.WriteLine(message);
  ```

  ```go Go
  client := anthropic.NewClient()

  response, err := client.Messages.New(context.TODO(), anthropic.MessageNewParams{
  	Model:     anthropic.ModelClaudeSonnet4_5,
  	MaxTokens: 1,
  	Messages: []anthropic.MessageParam{
  		anthropic.NewUserMessage(anthropic.NewTextBlock("What is latin for Ant? (A) Apoidea, (B) Rhopalocera, (C) Formicidae")),
  		anthropic.NewAssistantMessage(anthropic.NewTextBlock("The answer is (")),
  	},
  })
  if err != nil {
  	log.Fatal(err)
  }
  fmt.Println(response)
  ```

  ```java Java
  AnthropicClient client = AnthropicOkHttpClient.fromEnv();

  MessageCreateParams params = MessageCreateParams.builder()
      .model(Model.CLAUDE_SONNET_4_5)
      .maxTokens(1L)
      .addUserMessage("What is latin for Ant? (A) Apoidea, (B) Rhopalocera, (C) Formicidae")
      .addAssistantMessage("The answer is (")
      .build();

  Message response = client.messages().create(params);
  System.out.println(response);
  ```

  ```php PHP
  $client = new Client();

  $message = $client->messages->create(
      maxTokens: 1,
      messages: [
          ['role' => 'user', 'content' => 'What is latin for Ant? (A) Apoidea, (B) Rhopalocera, (C) Formicidae'],
          ['role' => 'assistant', 'content' => 'The answer is ('],
      ],
      model: 'claude-sonnet-4-5',
  );
  echo $message->content[0]->text;
  ```

  ```ruby Ruby
  client = Anthropic::Client.new

  message = client.messages.create(
    model: "claude-sonnet-4-5",
    max_tokens: 1,
    messages: [
      {
        role: "user",
        content: "What is latin for Ant? (A) Apoidea, (B) Rhopalocera, (C) Formicidae"
      },
      { role: "assistant", content: "The answer is (" }
    ]
  )
  puts message
  ```
</CodeGroup>

```json Output
{
  "id": "msg_01Q8Faay6S7QPTvEUUQARt7h",
  "type": "message",
  "role": "assistant",
  "content": [
    {
      "type": "text",
      "text": "C"
    }
  ],
  "model": "claude-sonnet-4-5",
  "stop_reason": "max_tokens",
  "stop_sequence": null,
  "usage": {
    "input_tokens": 42,
    "output_tokens": 1
  }
}
```

## Vision

Claude can read both text and images in requests. You can supply images using the `base64`, `url`, or `file` source types. The `file` source type references an image uploaded through the [Files API](https://platform.claude.com/docs/en/build-with-claude/files). Supported media types are `image/jpeg`, `image/png`, `image/gif`, and `image/webp`. See the [vision guide](https://platform.claude.com/docs/en/build-with-claude/vision) for more details.

<CodeGroup>
  ```bash cURL
  #!/bin/sh

  # Option 1: Base64-encoded image
  IMAGE_BASE64=$(curl "https://platform.claude.com/docs/images/vision-example.jpg" | base64 | tr -d '\n')

  curl https://api.anthropic.com/v1/messages \
    -H "x-api-key: $ANTHROPIC_API_KEY" \
    -H "anthropic-version: 2023-06-01" \
    -H "content-type: application/json" \
    -d @- <<EOF
  {
    "model": "claude-opus-5-5",
    "max_tokens": 1024,
    "messages": [
      {"role": "user", "content": [
        {"type": "image", "source": {
          "type": "base64",
          "media_type": "image/jpeg",
          "data": "$IMAGE_BASE64"
        }},
        {"type": "text", "text": "What is in the above image?"}
      ]}
    ]
  }
  EOF

  # Option 2: URL-referenced image
  curl https://api.anthropic.com/v1/messages \
    -H "x-api-key: $ANTHROPIC_API_KEY" \
    -H "anthropic-version: 2023-06-01" \
    -H "content-type: application/json" \
    -d '{
      "model": "claude-opus-5-5",
      "max_tokens": 1024,
      "messages": [
        {"role": "user", "content": [
          {"type": "image", "source": {
            "type": "url",
            "url": "https://platform.claude.com/docs/images/vision-example.jpg"
          }},
          {"type": "text", "text": "What is in the above image?"}
        ]}
      ]
    }'
  ```

  ```bash CLI
  # Option 1: Base64-encoded image (CLI auto-encodes binary @file refs)
  curl -s "https://platform.claude.com/docs/images/vision-example.jpg" -o ./vision-example.jpg

  ant messages create <<'YAML'
  model: claude-opus-5-5
  max_tokens: 1024
  messages:
    - role: user
      content:
        - type: image
          source:
            type: base64
            media_type: image/jpeg
            data: "@./vision-example.jpg"
        - type: text
          text: What is in the above image?
  YAML

  # Option 2: URL-referenced image
  ant messages create <<'YAML'
  model: claude-opus-5-5
  max_tokens: 1024
  messages:
    - role: user
      content:
        - type: image
          source:
            type: url
            url: https://platform.claude.com/docs/images/vision-example.jpg
        - type: text
          text: What is in the above image?
  YAML
  ```

  ```python Python
  import base64
  import httpx2

  # Option 1: Base64-encoded image
  image_url = "https://platform.claude.com/docs/images/vision-example.jpg"
  image_media_type = "image/jpeg"
  image_data = base64.standard_b64encode(httpx2.get(image_url).content).decode("utf-8")

  message = anthropic.Anthropic().messages.create(
      model="claude-opus-5-5",
      max_tokens=1024,
      messages=[
          {
              "role": "user",
              "content": [
                  {
                      "type": "image",
                      "source": {
                          "type": "base64",
                          "media_type": image_media_type,
                          "data": image_data,
                      },
                  },
                  {"type": "text", "text": "What is in the above image?"},
              ],
          }
      ],
  )
  print(message)

  # Option 2: URL-referenced image
  message_from_url = anthropic.Anthropic().messages.create(
      model="claude-opus-5-5",
      max_tokens=1024,
      messages=[
          {
              "role": "user",
              "content": [
                  {
                      "type": "image",
                      "source": {
                          "type": "url",
                          "url": "https://platform.claude.com/docs/images/vision-example.jpg",
                      },
                  },
                  {"type": "text", "text": "What is in the above image?"},
              ],
          }
      ],
  )
  print(message_from_url)
  ```

  ```typescript TypeScript
  const anthropic = new Anthropic();

  // Option 1: Base64-encoded image
  const imageUrl = "https://platform.claude.com/docs/images/vision-example.jpg";
  const imageMediaType = "image/jpeg";
  const imageArrayBuffer = await (await fetch(imageUrl)).arrayBuffer();
  const imageData = Buffer.from(imageArrayBuffer).toString("base64");

  const message = await anthropic.messages.create({
    model: "claude-opus-5-5",
    max_tokens: 1024,
    messages: [
      {
        role: "user",
        content: [
          {
            type: "image",
            source: {
              type: "base64",
              media_type: imageMediaType,
              data: imageData
            }
          },
          {
            type: "text",
            text: "What is in the above image?"
          }
        ]
      }
    ]
  });
  console.log(message);

  // Option 2: URL-referenced image
  const messageFromUrl = await anthropic.messages.create({
    model: "claude-opus-5-5",
    max_tokens: 1024,
    messages: [
      {
        role: "user",
        content: [
          {
            type: "image",
            source: {
              type: "url",
              url: "https://platform.claude.com/docs/images/vision-example.jpg"
            }
          },
          {
            type: "text",
            text: "What is in the above image?"
          }
        ]
      }
    ]
  });
  console.log(messageFromUrl);
  ```

  ```csharp C#
  using System.Collections.Generic;
  using System.Net.Http;
  using Anthropic;
  using Anthropic.Models.Messages;

  AnthropicClient client = new();

  // Option 1: Base64-encoded image
  string imageUrl = "https://platform.claude.com/docs/images/vision-example.jpg";

  using HttpClient httpClient = new();
  byte[] imageBytes = await httpClient.GetByteArrayAsync(imageUrl);
  string imageData = Convert.ToBase64String(imageBytes);

  var parameters = new MessageCreateParams
  {
      Model = Model.ClaudeOpus5_5,
      MaxTokens = 1024,
      Messages =
      [
          new()
          {
              Role = Role.User,
              Content = new MessageParamContent(new List<ContentBlockParam>
              {
                  new ContentBlockParam(new ImageBlockParam(
                      new ImageBlockParamSource(new Base64ImageSource()
                      {
                          Data = imageData,
                          MediaType = MediaType.ImageJpeg,
                      })
                  )),
                  new ContentBlockParam(new TextBlockParam("What is in the above image?")),
              }),
          }
      ]
  };

  var message = await client.Messages.Create(parameters);
  Console.WriteLine(message);

  // Option 2: URL-referenced image
  var parametersFromUrl = new MessageCreateParams
  {
      Model = Model.ClaudeOpus5_5,
      MaxTokens = 1024,
      Messages =
      [
          new()
          {
              Role = Role.User,
              Content = new MessageParamContent(new List<ContentBlockParam>
              {
                  new ContentBlockParam(new ImageBlockParam(
                      new ImageBlockParamSource(new UrlImageSource()
                      {
                          Url = "https://platform.claude.com/docs/images/vision-example.jpg",
                      })
                  )),
                  new ContentBlockParam(new TextBlockParam("What is in the above image?")),
              }),
          }
      ]
  };

  var messageFromUrl = await client.Messages.Create(parametersFromUrl);
  Console.WriteLine(messageFromUrl);
  ```

  ```go Go
  client := anthropic.NewClient()

  // Option 1: Base64-encoded image
  imageURL := "https://platform.claude.com/docs/images/vision-example.jpg"

  req, err := http.NewRequest("GET", imageURL, nil)
  if err != nil {
  	log.Fatal(err)
  }
  req.Header.Set("User-Agent", "AnthropicDocsBot/1.0")

  resp, err := http.DefaultClient.Do(req)
  if err != nil {
  	log.Fatal(err)
  }
  defer resp.Body.Close()

  imageBytes, err := io.ReadAll(resp.Body)
  if err != nil {
  	log.Fatal(err)
  }
  imageData := base64.StdEncoding.EncodeToString(imageBytes)

  message, err := client.Messages.New(context.TODO(), anthropic.MessageNewParams{
  	Model:     anthropic.ModelClaudeOpus5_5,
  	MaxTokens: 1024,
  	Messages: []anthropic.MessageParam{
  		anthropic.NewUserMessage(
  			anthropic.NewImageBlockBase64("image/jpeg", imageData),
  			anthropic.NewTextBlock("What is in the above image?"),
  		),
  	},
  })
  if err != nil {
  	log.Fatal(err)
  }
  fmt.Println(message)

  // Option 2: URL-referenced image
  messageFromURL, err := client.Messages.New(context.TODO(), anthropic.MessageNewParams{
  	Model:     anthropic.ModelClaudeOpus5_5,
  	MaxTokens: 1024,
  	Messages: []anthropic.MessageParam{
  		anthropic.NewUserMessage(
  			anthropic.NewImageBlock(anthropic.URLImageSourceParam{
  				URL: "https://platform.claude.com/docs/images/vision-example.jpg",
  			}),
  			anthropic.NewTextBlock("What is in the above image?"),
  		),
  	},
  })
  if err != nil {
  	log.Fatal(err)
  }
  fmt.Println(messageFromURL)
  ```

  ```java Java
  AnthropicClient client = AnthropicOkHttpClient.fromEnv();

  // Option 1: Base64-encoded image
  String imageUrl = "https://platform.claude.com/docs/images/vision-example.jpg";

  HttpClient httpClient = HttpClient.newHttpClient();
  HttpRequest request = HttpRequest.newBuilder().uri(URI.create(imageUrl)).build();
  HttpResponse<byte[]> response = httpClient.send(request, HttpResponse.BodyHandlers.ofByteArray());
  String imageData = Base64.getEncoder().encodeToString(response.body());

  List<ContentBlockParam> base64Content = List.of(
      ContentBlockParam.ofImage(
          ImageBlockParam.builder()
              .source(Base64ImageSource.builder()
                  .data(imageData)
                  .mediaType(Base64ImageSource.MediaType.IMAGE_JPEG)
                  .build())
              .build()),
      ContentBlockParam.ofText(
          TextBlockParam.builder()
              .text("What is in the above image?")
              .build())
  );

  Message message = client.messages().create(
      MessageCreateParams.builder()
          .model(Model.CLAUDE_OPUS_5_5)
          .maxTokens(1024L)
          .addUserMessageOfBlockParams(base64Content)
          .build());
  System.out.println(message);

  // Option 2: URL-referenced image
  List<ContentBlockParam> urlContent = List.of(
      ContentBlockParam.ofImage(
          ImageBlockParam.builder()
              .source(UrlImageSource.builder()
                  .url("https://platform.claude.com/docs/images/vision-example.jpg")
                  .build())
              .build()),
      ContentBlockParam.ofText(
          TextBlockParam.builder()
              .text("What is in the above image?")
              .build())
  );

  Message messageFromUrl = client.messages().create(
      MessageCreateParams.builder()
          .model(Model.CLAUDE_OPUS_5_5)
          .maxTokens(1024L)
          .addUserMessageOfBlockParams(urlContent)
          .build());
  System.out.println(messageFromUrl);
  ```

  ```php PHP
  $client = new Client();

  // Option 1: Base64-encoded image
  $image_url = 'https://platform.claude.com/docs/images/vision-example.jpg';
  $image_media_type = "image/jpeg";
  $image_data = base64_encode(file_get_contents($image_url));

  $message = $client->messages->create(
      maxTokens: 1024,
      messages: [
          [
              'role' => 'user',
              'content' => [
                  [
                      'type' => 'image',
                      'source' => [
                          'type' => 'base64',
                          'media_type' => $image_media_type,
                          'data' => $image_data,
                      ],
                  ],
                  [
                      'type' => 'text',
                      'text' => 'What is in the above image?',
                  ],
              ],
          ],
      ],
      model: 'claude-opus-5-5',
  );
  echo $message;

  // Option 2: URL-referenced image
  $message_from_url = $client->messages->create(
      maxTokens: 1024,
      messages: [
          [
              'role' => 'user',
              'content' => [
                  [
                      'type' => 'image',
                      'source' => [
                          'type' => 'url',
                          'url' => 'https://platform.claude.com/docs/images/vision-example.jpg',
                      ],
                  ],
                  [
                      'type' => 'text',
                      'text' => 'What is in the above image?',
                  ],
              ],
          ],
      ],
      model: 'claude-opus-5-5',
  );
  echo $message_from_url;
  ```

  ```ruby Ruby
  require "base64"
  require "net/http"

  client = Anthropic::Client.new

  # Option 1: Base64-encoded image
  image_url = "https://platform.claude.com/docs/images/vision-example.jpg"
  image_media_type = "image/jpeg"
  image_data = Base64.strict_encode64(Net::HTTP.get(URI(image_url)))

  message = client.messages.create(
    model: "claude-opus-5-5",
    max_tokens: 1024,
    messages: [
      {
        role: "user",
        content: [
          {
            type: "image",
            source: {
              type: "base64",
              media_type: image_media_type,
              data: image_data
            }
          },
          {
            type: "text",
            text: "What is in the above image?"
          }
        ]
      }
    ]
  )
  puts message

  # Option 2: URL-referenced image
  message_from_url = client.messages.create(
    model: "claude-opus-5-5",
    max_tokens: 1024,
    messages: [
      {
        role: "user",
        content: [
          {
            type: "image",
            source: {
              type: "url",
              url: "https://platform.claude.com/docs/images/vision-example.jpg"
            }
          },
          {
            type: "text",
            text: "What is in the above image?"
          }
        ]
      }
    ]
  )
  puts message_from_url
  ```
</CodeGroup>

```json Output
{
  "id": "msg_011CdKmWtV3oFx1C5yUbf5CY",
  "type": "message",
  "role": "assistant",
  "content": [
    {
      "type": "text",
      "text": "This image is a beautiful minimalist/flat-design illustration of a sunset landscape. Here's what it contains:\n\n**Sky & Sun:**\n- A warm gradient sky transitioning from golden-yellow at the top to deep orange toward the horizon\n- A large pale yellow sun positioned in the upper-right area\n\n**Birds:**\n- Three small silhouetted birds flying in the upper-left portion of the sky, depicted as simple \"M\" or \"v\" shapes\n\n**Mountains:**\n- Multiple layered mountain peaks in purple and maroon tones\n- The mountains overlap to create depth, with varying shades of dusty purple and deep burgundy\n\n**Water:**\n- A dark purple body of water at the bottom of the image\n- A reflection of the sun shown as horizontal cream/peach colored lines in the center-bottom area\n\nThe overall style is clean, geometric, and uses a warm sunset color palette (oranges, yellows, purples, and maroons), giving it a peaceful, serene aesthetic typical of modern vector/flat design artwork."
    }
  ],
  "model": "claude-opus-5-5",
  "stop_reason": "end_turn",
  "stop_sequence": null,
  "usage": {
    "input_tokens": 1030,
    "output_tokens": 350
  }
}
```

## Next steps

<CardGroup cols={2}>
  <Card title="Stop reasons and fallback" icon="list" href="https://platform.claude.com/docs/en/build-with-claude/handling-stop-reasons">
    Handle each `stop_reason` value and decide what to do when a response ends.
  </Card>

  <Card title="Tool use with Claude" icon="wrench" href="https://platform.claude.com/docs/en/agents-and-tools/tool-use/overview">
    Give Claude tools to call external services and APIs from within the Messages API.
  </Card>

  <Card title="Computer use tool" icon="computer" href="https://platform.claude.com/docs/en/agents-and-tools/tool-use/computer-use-tool">
    Control desktop computer environments with the Messages API.
  </Card>

  <Card title="Browser use tool" icon="browser" href="https://platform.claude.com/docs/en/agents-and-tools/tool-use/browser-use-tool">
    Let Claude navigate, read, and interact with webpages in a browser you run.
  </Card>

  <Card title="Structured outputs" icon="code-brackets" href="https://platform.claude.com/docs/en/build-with-claude/structured-outputs">
    Get guaranteed, schema-validated JSON output from Claude.
  </Card>

  <Card title="Task budgets" icon="gauge" href="https://platform.claude.com/docs/en/build-with-claude/task-budgets">
    Set an advisory token budget across a full agentic loop with `output_config.task_budget`.
  </Card>
</CardGroup>