llms-full.txt

# mcp-annotated-java-sdk

Annotation-driven MCP (Model Context Protocol) SDK for Java that simplifies MCP server development.

## Overview

This SDK is a lightweight, annotation-based framework that simplifies MCP server development in Java. Define, develop and integrate your MCP Resources / Prompts / Tools with minimal code - No Spring Framework Required.

## What is MCP?

The Model Context Protocol (MCP) is a standardized protocol for building servers that expose data and functionality to LLM applications. Think of it like a web API, but specifically designed for LLM interactions.

## Key Advantages

- **No Spring Framework Required** - Pure Java, lightweight and fast
- **Instant MCP Server** - Get your server running with just 1 line of code
- **Zero Boilerplate** - No need to write low-level MCP SDK code
- **No JSON Schema** - Forget about complex and lengthy JSON definitions
- **Focus on Logic** - Concentrate on your core business logic
- **Spring AI Compatible** - Configuration file compatible with Spring AI Framework
- **Multilingual Support** - Built-in i18n support for MCP components
- **Type-Safe** - Leverage Java's type system for compile-time safety

## Comparison with Official MCP Java SDK

| Feature | Official MCP SDK | This SDK |
|---------|------------------|----------|
| Code Required | ~50-100 lines | ~5-10 lines |
| JSON Schema | Hand-coded JSON | No need to care |
| Type Safety | Limited | Full |
| Learning Curve | Steep | Gentle |
| Multilingual | Unsupported | Supported |

## Requirements

- **Java 17 or later** (required by official MCP Java SDK)

## Installation

### Maven

```xml
<dependency>
    <groupId>io.github.thought2code</groupId>
    <artifactId>mcp-annotated-java-sdk</artifactId>
    <version>0.14.0</version>
</dependency>
```

### Gradle

```gradle
implementation 'io.github.thought2code:mcp-annotated-java-sdk:0.14.0'
```

## Quick Start Tutorial

### Step 1: Create Configuration File

Create `mcp-server.yml` in your `src/main/resources`:

```yaml
enabled: true
mode: STDIO
name: my-first-mcp-server
version: 1.0.0
type: SYNC
instructions: You are a helpful AI assistant
request-timeout: 20000
capabilities:
  resource: true
  prompt: true
  tool: true
change-notification:
  resource: true
  prompt: true
  tool: true
```

### Step 2: Create MCP Server Main Class

```java
@McpServerApplication
public class MyFirstMcpServer {
    public static void main(String[] args) {
        McpApplication.run(MyFirstMcpServer.class, args);
    }
}
```

### Step 3: Define MCP Resources (Optional)

```java
public class MyResources {
    @McpResource(uri = "system://info", description = "System information")
    public Map<String, String> getSystemInfo() {
        Map<String, String> info = new HashMap<>();
        info.put("os", System.getProperty("os.name"));
        info.put("java", System.getProperty("java.version"));
        info.put("cores", String.valueOf(Runtime.getRuntime().availableProcessors()));
        return info;
    }
}
```

### Step 4: Define MCP Tools

```java
public class MyTools {
    @McpTool(description = "Calculate the sum of two numbers")
    public int add(
        @McpToolParam(name = "a", description = "First number") int a,
        @McpToolParam(name = "b", description = "Second number") int b
    ) {
        return a + b;
    }

    @McpTool(description = "Read complete file contents with UTF-8 encoding")
    public String readFile(
        @McpToolParam(name = "path", description = "File path") String path
    ) {
        try {
            return Files.readString(Path.of(path));
        } catch (IOException e) {
            return "Error reading file: " + e.getMessage();
        }
    }
}
```

### Step 5: Define MCP Prompts (Optional)

```java
public class MyPrompts {
    @McpPrompt(description = "Generate code for a given task")
    public String generateCode(
        @McpPromptParam(name = "language", description = "Programming language") String language,
        @McpPromptParam(name = "task", description = "Task description") String task
    ) {
        return String.format("Write %s code to: %s", language, task);
    }

    @McpPrompt(description = "Format text as specified style")
    public String formatText(
        @McpPromptParam(name = "text", description = "Text to format") String text,
        @McpPromptParam(name = "style", description = "Format style (e.g., formal, casual, technical)") String style
    ) {
        return String.format("Rewrite the following text in a %s style: %s", style, text);
    }
}
```

### Step 6: Run the Server

```bash
# Compile your project
./mvnw clean package
```

Run `MyFirstMcpServer` from your IDE, or use `java -cp ...` with your compiled classes and dependencies on the classpath. Use an executable JAR setup in your own project if you need `java -jar` with a single file.

## Core Components

### Resources

Resource components are used to expose data to LLMs, similar to GET requests in Web APIs.

#### @McpResource Parameters

| Parameter | Description | Required |
|-----------|-------------|----------|
| `uri` | Unique identifier of the resource (URI format) | Yes |
| `description` | Resource description for LLM understanding | No (defaults to `name`, then method name) |
| `name` | Resource name (defaults to method name) | No |
| `title` | Resource title (defaults to `name`) | No |
| `mimeType` | MIME type of the resource content | No (default `text/plain`) |

### Tools

Tool components are used to execute operations or calculations, similar to POST requests in Web APIs.

#### @McpTool Parameters

| Parameter | Description | Required |
|-----------|-------------|----------|
| `description` | Tool description for LLM understanding | No (defaults to tool `name`, then method name) |
| `name` | Tool name (defaults to method name) | No |
| `title` | Tool title for display purposes | No |

#### @McpToolParam Parameters

| Parameter | Description | Required |
|-----------|-------------|----------|
| `name` | Parameter name | Yes |
| `description` | Parameter description | No (defaults to `name`) |
| `required` | Whether the parameter is required | No (default `true`) |

### Prompts

Prompt components are used to define reusable prompt templates.

#### @McpPrompt Parameters

| Parameter | Description | Required |
|-----------|-------------|----------|
| `description` | Prompt description for LLM understanding | No (defaults to prompt `name`, then method name) |
| `name` | Prompt name (defaults to method name) | No |
| `title` | Prompt title for display purposes | No |

#### @McpPromptParam Parameters

| Parameter | Description | Required |
|-----------|-------------|----------|
| `name` | Parameter name | Yes |
| `description` | Parameter description | No (defaults to `name`) |
| `required` | Whether the parameter is required | No (default `true`) |

### Completions

Completions provide auto-complete suggestions for resource URIs and prompt arguments.

Handlers must **return** `McpCompleteCompletion` and take **exactly one** parameter of type `McpSchema.CompleteRequest.CompleteArgument` (`name()` and `value()` identify the argument being completed).

#### Resource Completions

```java
import com.github.thought2code.mcp.annotated.annotation.McpResourceCompletion;
import com.github.thought2code.mcp.annotated.server.component.McpCompleteCompletion;
import io.modelcontextprotocol.spec.McpSchema;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.List;
import java.util.stream.Collectors;

@McpResourceCompletion(uri = "file://")
public McpCompleteCompletion completeFileUri(McpSchema.CompleteRequest.CompleteArgument argument) {
  String prefix = argument.value() != null ? argument.value() : "";
  try {
    List<String> paths =
        Files.list(Paths.get(prefix.isEmpty() ? "." : prefix))
            .map(Path::toString)
            .limit(50)
            .collect(Collectors.toList());
    return McpCompleteCompletion.builder()
        .values(paths)
        .total(paths.size())
        .hasMore(false)
        .build();
  } catch (Exception e) {
    return McpCompleteCompletion.empty();
  }
}
```

#### Prompt Completions

`@McpPromptCompletion.name` must match the **registered prompt name** (by default, the Java method name of the `@McpPrompt` method). Filter by `argument.name()` when one prompt has multiple parameters.

```java
import com.github.thought2code.mcp.annotated.annotation.McpPromptCompletion;
import com.github.thought2code.mcp.annotated.server.component.McpCompleteCompletion;
import io.modelcontextprotocol.spec.McpSchema;
import java.util.List;

@McpPromptCompletion(name = "generateCode")
public McpCompleteCompletion completeGenerateCode(McpSchema.CompleteRequest.CompleteArgument argument) {
  if (!"language".equals(argument.name())) {
    return McpCompleteCompletion.empty();
  }
  return McpCompleteCompletion.builder()
      .values(List.of("Java", "Python", "JavaScript", "Go", "Rust"))
      .total(5)
      .hasMore(false)
      .build();
}
```

## Server Modes

If `mode` is omitted in `mcp-server.yml`, the server defaults to **STREAMABLE**.

| Mode | Description | Use Case |
|------|-------------|----------|
| **STDIO** | Standard input/output communication | CLI tools, local development |
| **SSE** | Server-Sent Events (HTTP-based) | Real-time web applications (deprecated) |
| **STREAMABLE** | HTTP streaming | Web applications, recommended for production |

### STDIO Mode

```yaml
mode: STDIO
```

### SSE Mode (Deprecated)

```yaml
mode: SSE
sse:
  port: 8080
  endpoint: /sse
  message-endpoint: /mcp/message
  base-url: http://localhost:8080
```

### STREAMABLE Mode

```yaml
mode: STREAMABLE
streamable:
  mcp-endpoint: /mcp/message
  disallow-delete: false
  keep-alive-interval: 20000
  port: 8080
```

## Configuration Properties

| Property | Description | Default |
|----------|-------------|---------|
| `enabled` | Enable/disable MCP server | `true` |
| `mode` | Server mode: `STDIO`, `SSE`, `STREAMABLE` | `STREAMABLE` |
| `name` | Server name | `mcp-server` |
| `version` | Server version | `1.0.0` |
| `type` | Server type: `SYNC`, `ASYNC` | `SYNC` |
| `instructions` | Instructions for the LLM client | (empty) |
| `request-timeout` | Request timeout in milliseconds | `20000` |
| `capabilities.resource` | Enable resource support | `true` |
| `capabilities.subscribe-resource` | Enable resource subscription | `true` |
| `capabilities.prompt` | Enable prompt support | `true` |
| `capabilities.tool` | Enable tool support | `true` |
| `capabilities.completion` | Enable completion support | `true` |
| `change-notification.resource` | Notify clients on resource change | `true` |
| `change-notification.prompt` | Notify clients on prompt change | `true` |
| `change-notification.tool` | Notify clients on tool change | `true` |
| `sse.message-endpoint` | SSE POST message path | `/mcp/message` |
| `sse.endpoint` | SSE stream path | `/sse` |
| `sse.base-url` | Public base URL for the SSE server | *(empty)* |
| `sse.port` | HTTP port for SSE mode | `8080` |
| `streamable.mcp-endpoint` | Streamable HTTP MCP path | `/mcp/message` |
| `streamable.disallow-delete` | Reject HTTP DELETE on session | `false` |
| `streamable.keep-alive-interval` | Keep-alive interval (ms) | `20000` |
| `streamable.port` | HTTP port for STREAMABLE mode | `8080` |

## Profile-based Configuration

```yaml
# mcp-server.yml (base configuration)
enabled: true
mode: STREAMABLE
name: my-mcp-server
version: 1.0.0
profile: dev
```

```yaml
# mcp-server-dev.yml (profile-specific configuration)
streamable:
  port: 8080
```

## Multilingual Support (i18n)

### Enable i18n

```java
@McpServerApplication
@McpI18nEnabled(resourceBundleBaseName = "messages")
public class I18nMcpServer {
    public static void main(String[] args) {
        McpApplication.run(I18nMcpServer.class, args);
    }
}
```

### Create Resource Bundles

```properties
# messages.properties
tool.add.description=Calculate the sum of two numbers
tool.add.param.a.description=First number
tool.add.param.b.description=Second number
```

```properties
# messages_zh_CN.properties
tool.add.description=计算两个数字的和
tool.add.param.a.description=第一个数字
tool.add.param.b.description=第二个数字
```

### Use i18n in Components

```java
@McpTool(description = "tool.add.description")
public int add(
    @McpToolParam(name = "a", description = "tool.add.param.a.description") int a,
    @McpToolParam(name = "b", description = "tool.add.param.b.description") int b
) {
    return a + b;
}
```

## Structured Content

Tools can return structured content by returning a type that **implements** `McpStructuredContent` (often a `record` with `@McpJsonSchemaProperty` on fields). There is no `McpStructuredContent.of(...)` helper.

```java
import com.github.thought2code.mcp.annotated.annotation.McpJsonSchemaDefinition;
import com.github.thought2code.mcp.annotated.annotation.McpJsonSchemaProperty;
import com.github.thought2code.mcp.annotated.annotation.McpTool;
import com.github.thought2code.mcp.annotated.annotation.McpToolParam;
import com.github.thought2code.mcp.annotated.server.McpStructuredContent;

@McpJsonSchemaDefinition
public record User(
    @McpJsonSchemaProperty(description = "User id") String id,
    @McpJsonSchemaProperty(description = "Display name") String name)
    implements McpStructuredContent {

  @Override
  public String asTextContent() {
    return "User " + id + ": " + name;
  }
}

@McpTool(description = "Get user details")
public User getUser(@McpToolParam(name = "id", description = "User ID") String id) {
  return new User(id, "Ada");
}
```

## Error Handling

If a tool method **throws any exception**, the server returns a `CallToolResult` with `isError` set to `true` and a generic method-invocation error message (the exception message is not forwarded to the client today).

For expected failures such as validation, return a normal value (for example a `String`) so the tool call remains a successful result with `isError` false:

```java
@McpTool(description = "Divide two numbers")
public String divide(
    @McpToolParam(name = "a", description = "Dividend") double a,
    @McpToolParam(name = "b", description = "Divisor") double b) {
  if (b == 0) {
    return "Cannot divide by zero.";
  }
  return Double.toString(a / b);
}
```

## Automatic Registration

After defining MCP components, they will be automatically registered to the server. You just need to ensure that the component classes are in the package scanning path of the server application.

### Specify Package Path

```java
@McpServerApplication(basePackageClass = MyMcpServer.class)
// or
@McpServerApplication(basePackage = "com.example.mcp.components")
```

If no package path is specified, the package containing the main method will be scanned.

## Project Structure

```
your-mcp-project/
├── pom.xml
├── src/
│   ├── main/
│   │   ├── java/
│   │   │   └── com/
│   │   │       └── example/
│   │   │           ├── MyMcpServer.java         # Main entry point
│   │   │           ├── components/
│   │   │           │   ├── MyResources.java     # MCP Resources
│   │   │           │   ├── MyTools.java         # MCP Tools
│   │   │           │   └── MyPrompts.java       # MCP Prompts
│   │   │           └── service/
│   │   │               └── BusinessLogic.java   # Business logic
│   │   └── resources/
│   │       ├── mcp-server.yml                   # MCP configuration
│   │       └── messages.properties              # Internationalization messages
│   └── test/
│       └── java/
│           └── com/
│               └── example/
│                   └── McpServerTest.java       # Unit tests
└── target/
    └── *.jar                                    # Build output (name depends on your project)
```

## Custom JSON Schema

For complex tool parameter or result types, annotate the type with `@McpJsonSchemaDefinition` and annotate fields (or record components) with `@McpJsonSchemaProperty` (JSON types are inferred from Java types).

```java
import com.github.thought2code.mcp.annotated.annotation.McpJsonSchemaDefinition;
import com.github.thought2code.mcp.annotated.annotation.McpJsonSchemaProperty;
import com.github.thought2code.mcp.annotated.annotation.McpTool;
import com.github.thought2code.mcp.annotated.annotation.McpToolParam;

@McpJsonSchemaDefinition
public record CreateUserRequest(
    @McpJsonSchemaProperty(description = "User name") String name,
    @McpJsonSchemaProperty(description = "User age", required = false) int age,
    @McpJsonSchemaProperty(description = "Email address") String email) {}

@McpTool(description = "Create a user")
public String createUser(
    @McpToolParam(name = "user", description = "User payload") CreateUserRequest user) {
  return "Created: " + user.name();
}
```

## Important Notes

1. **Deprecated API**: The `McpServers` class is deprecated. Use `McpApplication.run()` instead.
2. **Deprecated Mode**: SSE mode is deprecated. Use STREAMABLE mode for new projects.
3. **Default Required**: The default `required` value for `@McpToolParam`, `@McpPromptParam`, and `@McpJsonSchemaProperty` is `true`.

## Links

- **GitHub Repository**: https://github.com/thought2code/mcp-annotated-java-sdk
- **Official Documentation**: https://thought2code.github.io/mcp-annotated-java-sdk-docs
- **Examples Repository**: https://github.com/thought2code/mcp-java-sdk-examples
- **MCP Official Site**: https://modelcontextprotocol.io
- **MCP Java SDK**: https://github.com/modelcontextprotocol/java-sdk

## License

MIT License