Other Official SDKs Basics

8 examples to get you started with the other official Claude SDKs - 5 basic and 3 intermediate.

Prerequisites

An Anthropic API key, set as the ANTHROPIC_API_KEY environment variable.
The SDK package for whichever language you're using, installed via that language's package manager (go get, Maven/Gradle, NuGet, Composer, or Bundler).
Nothing else - each example below is a complete, standalone program.

Basic Examples

1. First Call in Go

The simplest possible Messages API call using anthropic-sdk-go.

package main
 
import (
    "context"
    "fmt"
    "os"
 
    "github.com/anthropics/anthropic-sdk-go"
    "github.com/anthropics/anthropic-sdk-go/option"
)
 
func main() {
    client := anthropic.NewClient(
        option.WithAPIKey(os.Getenv("ANTHROPIC_API_KEY")),
    )
 
    message, err := client.Messages.New(context.Background(), anthropic.MessageNewParams{
        Model:     anthropic.ModelClaudeSonnet5,
        MaxTokens: 1024,
        Messages: []anthropic.MessageParam{
            anthropic.NewUserMessage(anthropic.NewTextBlock("Say hello in one sentence.")),
        },
    })
    if err != nil {
        panic(err)
    }
 
    fmt.Println(message.Content[0].Text)
}

anthropic.NewClient reads no config beyond the API key option; there's no separate "connect" step.
Errors come back as a normal Go error value, not an exception, so check err before touching message.
message.Content is a slice of content blocks; a plain text reply is Content[0].Text.

Related: Calling Claude from Go with the Official SDK - streaming and tool_use in Go

2. First Call in Java

The same call using the Java SDK's builder-style client.

import com.anthropic.client.AnthropicClient;
import com.anthropic.client.okhttp.AnthropicOkHttpClient;
import com.anthropic.models.messages.Message;
import com.anthropic.models.messages.MessageCreateParams;
import com.anthropic.models.messages.Model;
 
public class FirstCall {
    public static void main(String[] args) {
        AnthropicClient client = AnthropicOkHttpClient.fromEnv();
 
        MessageCreateParams params = MessageCreateParams.builder()
            .model(Model.CLAUDE_SONNET_5)
            .maxTokens(1024)
            .addUserMessage("Say hello in one sentence.")
            .build();
 
        Message message = client.messages().create(params);
        System.out.println(message.content().get(0).text().get());
    }
}

AnthropicOkHttpClient.fromEnv() reads ANTHROPIC_API_KEY from the environment automatically.
MessageCreateParams.builder() is Java's idiomatic way to assemble a request with optional fields.
A failed call throws a typed exception rather than returning an error value, so wrap this in a try/catch in real code.

3. First Call in C#

The same call using the C# SDK's typed request object and async/await.

using Anthropic.SDK;
using Anthropic.SDK.Messaging;
 
var client = new AnthropicClient(Environment.GetEnvironmentVariable("ANTHROPIC_API_KEY"));
 
var response = await client.Messages.GetClaudeMessageAsync(new MessageParameters
{
    Model = AnthropicModels.ClaudeSonnet5,
    MaxTokens = 1024,
    Messages = new List<Message>
    {
        new Message(RoleType.User, "Say hello in one sentence.")
    }
});
 
Console.WriteLine(response.Message);

The client is constructed directly with the API key rather than an options object.
GetClaudeMessageAsync follows .NET's async convention, so it must be awaited inside an async context.
MessageParameters mirrors the Messages API request body field-for-field, just as a typed C# object.

4. First Call in PHP

The same call using PHP's associative-array request style.

<?php
require 'vendor/autoload.php';
 
use Anthropic\Anthropic;
 
$client = Anthropic::factory()
    ->withApiKey(getenv('ANTHROPIC_API_KEY'))
    ->make();
 
$response = $client->messages()->create([
    'model' => 'claude-sonnet-5',
    'max_tokens' => 1024,
    'messages' => [
        ['role' => 'user', 'content' => 'Say hello in one sentence.'],
    ],
]);
 
echo $response->content[0]->text;

Anthropic::factory() is a fluent builder; withApiKey() and make() produce the configured client.
Request parameters are a plain associative array, matching the Messages API's JSON shape directly.
PHP has no compile-time type checking here, so a typo in a key name (like max_token) fails at request time, not before.

5. First Call in Ruby

The same call using Ruby's hash-based request style.

require "anthropic"
 
client = Anthropic::Client.new(api_key: ENV["ANTHROPIC_API_KEY"])
 
response = client.messages.create(
  model: "claude-sonnet-5",
  max_tokens: 1024,
  messages: [
    { role: "user", content: "Say hello in one sentence." }
  ]
)
 
puts response.content[0].text

Anthropic::Client.new takes the API key directly as a keyword argument.
Ruby hashes with symbol keys map cleanly onto the Messages API's JSON body, the same role as PHP's associative array.
Like PHP, there's no compile-time check on the request shape, so validate keys carefully in larger codebases.

Intermediate Examples

6. Reading the Response Shape in Go

Every SDK returns the same underlying fields; this example reads more of them.

message, err := client.Messages.New(context.Background(), anthropic.MessageNewParams{
    Model:     anthropic.ModelClaudeSonnet5,
    MaxTokens: 256,
    Messages: []anthropic.MessageParam{
        anthropic.NewUserMessage(anthropic.NewTextBlock("Name three Go standard library packages.")),
    },
})
if err != nil {
    panic(err)
}
 
fmt.Println("Stop reason:", message.StopReason)
fmt.Println("Input tokens:", message.Usage.InputTokens)
fmt.Println("Output tokens:", message.Usage.OutputTokens)
for _, block := range message.Content {
    if block.Type == "text" {
        fmt.Println(block.Text)
    }
}

StopReason tells you why generation stopped: end_turn, max_tokens, tool_use, and so on - check it before assuming the reply is complete.
Usage carries token counts for both sides of the exchange, which every SDK exposes in some typed or dictionary form.
Content is always a list of blocks even for a single text reply, because the same field also carries tool_use blocks.

Related: Messages API Basics - the request/response shape every SDK wraps

7. Setting a System Prompt Across Languages

The system parameter behaves identically everywhere; only the syntax to set it changes.

MessageCreateParams params = MessageCreateParams.builder()
    .model(Model.CLAUDE_SONNET_5)
    .maxTokens(512)
    .system("You are a terse, technical code reviewer. Answer in bullet points only.")
    .addUserMessage("Review this function signature: func Add(a, b int) int")
    .build();
 
Message message = client.messages().create(params);
System.out.println(message.content().get(0).text().get());

response = client.messages.create(
  model: "claude-sonnet-5",
  max_tokens: 512,
  system: "You are a terse, technical code reviewer. Answer in bullet points only.",
  messages: [
    { role: "user", content: "Review this function signature: func Add(a, b int) int" }
  ]
)

The system field is a top-level request parameter in every SDK, never a message in the messages array.
It steers tone and constraints for the whole conversation, not just the next reply.
Keep it stable across turns in a multi-turn conversation; changing it mid-conversation can produce inconsistent behavior.

8. Handling Errors Idiomatically Per Language

The same rate-limit failure, handled the way each language expects.

message, err := client.Messages.New(ctx, params)
if err != nil {
    var apiErr *anthropic.Error
    if errors.As(err, &apiErr) && apiErr.StatusCode == 429 {
        fmt.Println("Rate limited, back off and retry.")
        return
    }
    panic(err)
}

try
{
    var response = await client.Messages.GetClaudeMessageAsync(parameters);
}
catch (RateLimitException)
{
    Console.WriteLine("Rate limited, back off and retry.");
}

Go surfaces errors as values you inspect with errors.As, matching Go's no-exceptions convention.
C# and Java throw typed exceptions you catch by class, matching their platforms' conventions.
Whichever language you're in, the underlying condition (an HTTP 429 from the Messages API) is the same - only the catching mechanism differs.

Related: Idiomatic Tool Use Across Go, Java, C#, PHP, and Ruby - the same cross-language comparison, applied to tool_use

Stack versions: Written against the Claude model lineup current as of ~June 2026 - Claude Fable 5, Claude Opus 4.8, Claude Sonnet 5 (the default), and Claude Haiku 4.5 - and the current official SDKs for Go, Java, C#, PHP, and Ruby. Model names, SDK versions, and pricing move quickly - verify current specifics at platform.claude.com/docs before relying on them.

Prerequisites

An Anthropic API key, set as the ANTHROPIC_API_KEY environment variable.
The SDK package for whichever language you're using, installed via that language's package manager (go get, Maven/Gradle, NuGet, Composer, or Bundler).
Nothing else - each example below is a complete, standalone program.

Basic Examples

1. First Call in Go

The simplest possible Messages API call using anthropic-sdk-go.

package main
 
import (
    "context"
    "fmt"
    "os"
 
    "github.com/anthropics/anthropic-sdk-go"
    "github.com/anthropics/anthropic-sdk-go/option"
)
 
func main() {
    client := anthropic.NewClient(
        option.WithAPIKey(os.Getenv("ANTHROPIC_API_KEY")),
    )
 
    message, err := client.Messages.New(context.Background(), anthropic.MessageNewParams{
        Model:     anthropic.ModelClaudeSonnet5,
        MaxTokens: 1024,
        Messages: []anthropic.MessageParam{
            anthropic.NewUserMessage(anthropic.NewTextBlock("Say hello in one sentence.")),
        },
    })
    if err != nil {
        panic(err)
    }
 
    fmt.Println(message.Content[0].Text)
}

anthropic.NewClient reads no config beyond the API key option; there's no separate "connect" step.
Errors come back as a normal Go error value, not an exception, so check err before touching message.
message.Content is a slice of content blocks; a plain text reply is Content[0].Text.

Related: Calling Claude from Go with the Official SDK - streaming and tool_use in Go

2. First Call in Java

The same call using the Java SDK's builder-style client.

import com.anthropic.client.AnthropicClient;
import com.anthropic.client.okhttp.AnthropicOkHttpClient;
import com.anthropic.models.messages.Message;
import com.anthropic.models.messages.MessageCreateParams;
import com.anthropic.models.messages.Model;
 
public class FirstCall {
    public static void main(String[] args) {
        AnthropicClient client = AnthropicOkHttpClient.fromEnv();
 
        MessageCreateParams params = MessageCreateParams.builder()
            .model(Model.CLAUDE_SONNET_5)
            .maxTokens(1024)
            .addUserMessage("Say hello in one sentence.")
            .build();
 
        Message message = client.messages().create(params);
        System.out.println(message.content().get(0).text().get());
    }
}

AnthropicOkHttpClient.fromEnv() reads ANTHROPIC_API_KEY from the environment automatically.
MessageCreateParams.builder() is Java's idiomatic way to assemble a request with optional fields.
A failed call throws a typed exception rather than returning an error value, so wrap this in a try/catch in real code.

3. First Call in C#

The same call using the C# SDK's typed request object and async/await.

using Anthropic.SDK;
using Anthropic.SDK.Messaging;
 
var client = new AnthropicClient(Environment.GetEnvironmentVariable("ANTHROPIC_API_KEY"));
 
var response = await client.Messages.GetClaudeMessageAsync(new MessageParameters
{
    Model = AnthropicModels.ClaudeSonnet5,
    MaxTokens = 1024,
    Messages = new List<Message>
    {
        new Message(RoleType.User, "Say hello in one sentence.")
    }
});
 
Console.WriteLine(response.Message);

The client is constructed directly with the API key rather than an options object.
GetClaudeMessageAsync follows .NET's async convention, so it must be awaited inside an async context.
MessageParameters mirrors the Messages API request body field-for-field, just as a typed C# object.

4. First Call in PHP

The same call using PHP's associative-array request style.

<?php
require 'vendor/autoload.php';
 
use Anthropic\Anthropic;
 
$client = Anthropic::factory()
    ->withApiKey(getenv('ANTHROPIC_API_KEY'))
    ->make();
 
$response = $client->messages()->create([
    'model' => 'claude-sonnet-5',
    'max_tokens' => 1024,
    'messages' => [
        ['role' => 'user', 'content' => 'Say hello in one sentence.'],
    ],
]);
 
echo $response->content[0]->text;

Anthropic::factory() is a fluent builder; withApiKey() and make() produce the configured client.
Request parameters are a plain associative array, matching the Messages API's JSON shape directly.
PHP has no compile-time type checking here, so a typo in a key name (like max_token) fails at request time, not before.

5. First Call in Ruby

The same call using Ruby's hash-based request style.

require "anthropic"
 
client = Anthropic::Client.new(api_key: ENV["ANTHROPIC_API_KEY"])
 
response = client.messages.create(
  model: "claude-sonnet-5",
  max_tokens: 1024,
  messages: [
    { role: "user", content: "Say hello in one sentence." }
  ]
)
 
puts response.content[0].text

Anthropic::Client.new takes the API key directly as a keyword argument.
Ruby hashes with symbol keys map cleanly onto the Messages API's JSON body, the same role as PHP's associative array.
Like PHP, there's no compile-time check on the request shape, so validate keys carefully in larger codebases.

Intermediate Examples

6. Reading the Response Shape in Go

Every SDK returns the same underlying fields; this example reads more of them.

message, err := client.Messages.New(context.Background(), anthropic.MessageNewParams{
    Model:     anthropic.ModelClaudeSonnet5,
    MaxTokens: 256,
    Messages: []anthropic.MessageParam{
        anthropic.NewUserMessage(anthropic.NewTextBlock("Name three Go standard library packages.")),
    },
})
if err != nil {
    panic(err)
}
 
fmt.Println("Stop reason:", message.StopReason)
fmt.Println("Input tokens:", message.Usage.InputTokens)
fmt.Println("Output tokens:", message.Usage.OutputTokens)
for _, block := range message.Content {
    if block.Type == "text" {
        fmt.Println(block.Text)
    }
}

StopReason tells you why generation stopped: end_turn, max_tokens, tool_use, and so on - check it before assuming the reply is complete.
Usage carries token counts for both sides of the exchange, which every SDK exposes in some typed or dictionary form.
Content is always a list of blocks even for a single text reply, because the same field also carries tool_use blocks.

Related: Messages API Basics - the request/response shape every SDK wraps

7. Setting a System Prompt Across Languages

The system parameter behaves identically everywhere; only the syntax to set it changes.

MessageCreateParams params = MessageCreateParams.builder()
    .model(Model.CLAUDE_SONNET_5)
    .maxTokens(512)
    .system("You are a terse, technical code reviewer. Answer in bullet points only.")
    .addUserMessage("Review this function signature: func Add(a, b int) int")
    .build();
 
Message message = client.messages().create(params);
System.out.println(message.content().get(0).text().get());

response = client.messages.create(
  model: "claude-sonnet-5",
  max_tokens: 512,
  system: "You are a terse, technical code reviewer. Answer in bullet points only.",
  messages: [
    { role: "user", content: "Review this function signature: func Add(a, b int) int" }
  ]
)

The system field is a top-level request parameter in every SDK, never a message in the messages array.
It steers tone and constraints for the whole conversation, not just the next reply.
Keep it stable across turns in a multi-turn conversation; changing it mid-conversation can produce inconsistent behavior.

8. Handling Errors Idiomatically Per Language

The same rate-limit failure, handled the way each language expects.

message, err := client.Messages.New(ctx, params)
if err != nil {
    var apiErr *anthropic.Error
    if errors.As(err, &apiErr) && apiErr.StatusCode == 429 {
        fmt.Println("Rate limited, back off and retry.")
        return
    }
    panic(err)
}

try
{
    var response = await client.Messages.GetClaudeMessageAsync(parameters);
}
catch (RateLimitException)
{
    Console.WriteLine("Rate limited, back off and retry.");
}

Go surfaces errors as values you inspect with errors.As, matching Go's no-exceptions convention.
C# and Java throw typed exceptions you catch by class, matching their platforms' conventions.
Whichever language you're in, the underlying condition (an HTTP 429 from the Messages API) is the same - only the catching mechanism differs.

Related: Idiomatic Tool Use Across Go, Java, C#, PHP, and Ruby - the same cross-language comparison, applied to tool_use

Stack versions: Written against the Claude model lineup current as of ~June 2026 - Claude Fable 5, Claude Opus 4.8, Claude Sonnet 5 (the default), and Claude Haiku 4.5 - and the current official SDKs for Go, Java, C#, PHP, and Ruby. Model names, SDK versions, and pricing move quickly - verify current specifics at platform.claude.com/docs before relying on them.

Other Official SDKs Basics

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Other Official SDKs Basics