More SDKs and Code Examples

Besides Python, C# and TypeScript, there are official SDKs for Java, Go, Ruby and PHP. They all have the same shape: create a client (ANTHROPIC_API_KEY from the environment), call messages.create, then read the content blocks after checking their type.

12.1 Install commands

12.2 Java

import com.anthropic.client.AnthropicClient;
import com.anthropic.client.okhttp.AnthropicOkHttpClient;
import com.anthropic.models.messages.MessageCreateParams;
import com.anthropic.models.messages.Message;

AnthropicClient client = AnthropicOkHttpClient.fromEnv();   // ANTHROPIC_API_KEY

MessageCreateParams params = MessageCreateParams.builder()
    .model("claude-opus-5-5")
    .maxTokens(16000L)
    .addUserMessage("How does @Transactional work in Spring Boot?")
    .build();

Message response = client.messages().create(params);
response.content().stream()
    .flatMap(block -> block.text().stream())
    .forEach(t -> System.out.println(t.text()));

12.3 Go

import (
    "context"
    "fmt"
    "github.com/anthropics/anthropic-sdk-go/v2"
)

client := anthropic.NewClient()      // reads ANTHROPIC_API_KEY from the environment

resp, err := client.Messages.New(context.Background(), anthropic.MessageNewParams{
    Model:     "claude-opus-5-5",
    MaxTokens: 16000,
    Messages: []anthropic.MessageParam{
        anthropic.NewUserMessage(anthropic.NewTextBlock("Goroutine vs thread?")),
    },
})
if err != nil { log.Fatal(err) }
for _, block := range resp.Content {
    switch v := block.AsAny().(type) {
    case anthropic.TextBlock:
        fmt.Println(v.Text)
    }
}

12.4 Ruby and PHP

require "anthropic"
client = Anthropic::Client.new

message = client.messages.create(
  model: :"claude-opus-5-5", max_tokens: 16000,
  messages: [{ role: "user", content: "What is an N+1 query in Rails?" }]
)
message.content.each { |b| puts b.text if b.type == :text }   # type is a Symbol

use Anthropic\Client;
$client = new Client();

$message = $client->messages->create(
    model: 'claude-opus-5-5',
    maxTokens: 16000,                      // named args are camelCase in PHP
    messages: [['role' => 'user', 'content' => 'Explain Laravel queues']],
);
foreach ($message->content as $block) {
    if ($block->type === 'text') echo $block->text;
}

12.5 C# — Vision, Files API and Batches

using Anthropic;
using Anthropic.Core;
using Anthropic.Models.Files;
using Anthropic.Models.Messages;

AnthropicClient client = new();

// 1. Upload the file once
var upload = await client.Files.Upload(new FileUploadParams
{
    File = new BinaryContent
    {
        Stream = File.OpenRead("invoice.jpg"),
        FileName = "invoice.jpg",
        ContentType = new("image/jpeg"),
    },
});

// 2. Send the image by file_id
var response = await client.Messages.Create(new MessageCreateParams
{
    Model = Model.ClaudeOpus5_5,
    MaxTokens = 1024,
    Messages = [ new UserMessageParam {
        Content = new List<ContentBlockParam> {
            new ContentBlockParam(new ImageBlockParam(
                new ImageBlockParamSource(new FileImageSource(upload.ID)))),
            new ContentBlockParam(new TextBlockParam("What is the invoice total?")),
        },
    } ],
});

// Batch: 50% cheaper, async
var batch = await client.Messages.Batches.Create(new() {
    Requests = [
        new() { CustomID = "review-1",
                Params = new() { Model = "claude-haiku-5-5", MaxTokens = 200,
                                 Messages = [ new UserMessageParam { Content = "Sentiment: Great product!" } ] } },
    ],
});
// Poll client.Messages.Batches.Retrieve(batch.ID) until ProcessingStatus == "ended",
// then iterate client.Messages.Batches.Results(batch.ID) (match by CustomID).

12.6 Citations code (Python)

r = client.messages.create(
    model="claude-opus-5-5", max_tokens=2000,
    messages=[{"role": "user", "content": [
        {"type": "document",
         "source": {"type": "text", "media_type": "text/plain", "data": POLICY_TEXT},
         "title": "HR Leave Policy",
         "citations": {"enabled": True}},
        {"type": "text", "text": "How many days is maternity leave?"},
    ]}],
)
for b in r.content:
    if b.type == "text":
        print(b.text)
        for c in (b.citations or []):
            print("   ↳", c.cited_text)      # the exact quote from the document