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add Java resource reference doc
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‎articles/azure-functions/functions-bindings-mcp-resource-trigger.md‎

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> For C#, the Azure Functions MCP extension supports only the [isolated worker model](dotnet-isolated-process-guide.md).
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This first example shows how to use resource to implement the UI element of MCP Apps.
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> [!IMPORTANT]
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> The MCP extension in Java doesn't_ support resource today.
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Example code for JavaScript isn't currently available. See the TypeScript example for general guidance.
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The following example shows a Java function that serves an HTML weather widget as an MCP resource:
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```java
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@FunctionName("GetWeatherWidget")
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public String getWeatherWidget(
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@McpResourceTrigger(
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name = "context",
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uri = "ui://weather/index.html",
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resourceName = "Weather Widget",
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title = "Weather Widget",
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description = "Interactive weather display for MCP Apps",
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mimeType = "text/html;profile=mcp-app")
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@McpMetadata(
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name = "context",
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json = RESOURCE_METADATA)
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String context,
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final ExecutionContext executionContext) {
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executionContext.getLogger().info("GetWeatherWidget: serving weather widget UI");
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java.io.File file = new java.io.File("app/dist/index.html");
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if (file.exists()) {
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try {
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return java.nio.file.Files.readString(file.toPath(), StandardCharsets.UTF_8);
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} catch (IOException e) {
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executionContext.getLogger().log(Level.WARNING, "Failed to read UI from file", e);
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}
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}
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return "<html><body><p>Weather widget UI not found.</p></body></html>";
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}
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```
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The `RESOURCE_METADATA` constant is defined as a JSON string that provides additional MCP metadata surfaced via the protocol's `_meta` field:
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```java
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private static final String RESOURCE_METADATA = """
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{
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"ui": {
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"prefersBorder": true
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}
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}
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""";
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```
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[!INCLUDE [functions-mcp-extension-powershell-note](../../includes/functions-mcp-extension-powershell-note.md)]
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## Attributes
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Apply the `@McpResourceTrigger` annotation to a function parameter to define an MCP resource trigger.
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The `@McpResourceTrigger` annotation supports the following properties:
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| Property | Description |
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|---|---|
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| **`name`** | Required. The binding name for the resource invocation context parameter. |
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| **`uri`** | Required. The URI of the MCP resource (for example, `"file://readme.md"` or `"ui://weather/index.html"`). |
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| **`resourceName`** | Required. The display name of the MCP resource. |
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| **`title`** | Optional. A human-readable title for display purposes. Unlike `resourceName`, which is a programmatic identifier, this is a friendly label for UI presentation. |
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| **`description`** | Optional. A human-readable description of this resource. |
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| **`mimeType`** | Optional. The MIME type of the resource content (for example, `"text/plain"`, `"text/html"`, `"image/png"`, `"text/html;profile=mcp-app"`). |
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| **`size`** | Optional. The size of the resource in bytes. Defaults to `-1` (not specified). |
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| **`dataType`** | Optional. Defines how the Functions runtime should treat the parameter value. Possible values: `""` (default, deserialize to parameter type), `"string"`, `"binary"`. |
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## Metadata annotation
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You can optionally apply `@McpMetadata` on the same parameter as `@McpResourceTrigger` to attach arbitrary JSON metadata to the resource. This metadata is surfaced in the MCP protocol's `_meta` field when clients call `resources/list`.
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The `@McpMetadata` annotation supports the following properties:
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| Property | Description |
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|---|---|
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| **`name`** | Required. The binding parameter name. Should match the `name` value of the trigger annotation on the same parameter. |
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| **`json`** | Required. The metadata as a valid JSON string. Can include any arbitrary key-value pairs such as author information, version numbers, UI hints, or tags. |
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**Example:**
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```java
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@McpResourceTrigger(
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name = "context",
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uri = "file://readme.md",
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resourceName = "readme",
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description = "Application readme file",
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mimeType = "text/plain")
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@McpMetadata(
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name = "context",
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json = "{\"author\": \"John Doe\", \"version\": 1.0}")
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String context
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```
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## Setup
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Add the following dependency to your project's `pom.xml` file. The MCP annotations are included in the Azure Functions Java library starting from version **3.2.4**:
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```xml name=pom.xml
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<dependency>
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<groupId>com.microsoft.azure.functions</groupId>
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<artifactId>azure-functions-java-library</artifactId>
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<version>3.2.4</version>
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</dependency>
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```
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See the [Example section](#example) for complete examples.
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The MCP resource trigger binds the resource invocation context to a function parameter. The trigger can bind to the following types: `String`, or `byte[]` for binary content.
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### Resource URIs
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Use the `@McpMetadata` annotation to provide extra metadata for resources. This metadata is a JSON-serialized string included in the `meta` field of each resource when clients call `resources/list`. It can affect how the resource content is displayed or processed.
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### Return types
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The MCP resource trigger supports the following return types:
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| Type | Description |
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| --- | --- |
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| `String` | Returned as text content in the MCP `ReadResourceResult`. |
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| `byte[]` | Returned as base64-encoded binary content in the MCP `ReadResourceResult`. Set `dataType = "binary"` on the annotation when returning binary content. |
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### Resource discovery
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