Package akka.javasdk.annotations.mcp

Annotation Interface McpResource

@Target(METHOD) @Retention(RUNTIME) @Documented public @interface McpResource
Annotation to expose a method as an MCP resource that clients can fetch.

MCP resources provide static or dynamic content that AI models can access to gather information. Resources can be static files, configuration data, or dynamically generated content based on parameters.

Resource Types:

  • Static Resources: Use uri() for fixed content with no parameters
  • Dynamic Resources: Use uriTemplate() for parameterized content

Method Requirements:

  • Must be public
  • For static resources (uri): no parameters allowed
  • For dynamic resources (uriTemplate): parameters must match template placeholders
  • Must be in a class annotated with McpEndpoint

Return Types:

  • String: Returns as UTF-8 encoded text resource
  • byte[]: Returns as base64 encoded binary resource
  • Other types: Encoded to JSON with application/json MIME type

URI Templates: Templates can contain named placeholders for entire path segments only. Each placeholder must match a method parameter name. For example: "file:///images/{category}/{file}" matches file:///images/bicycles/tall_bike.jpg and passes "bicycles" as category and "tall_bike.jpg" as file.

Security: Always validate input parameters to prevent path traversal attacks or unauthorized access.

  • Element Details

    • uri

      String uri
      Returns:
      A unique URI identifying the resource. If this is defined uriTemplate must be empty.
      Default:
      ""

    • uriTemplate

      String uriTemplate
      Returns:
      A resource template path that can be used to create a URI that will identify a resource. If defined, uri must be empty, the URI template string can contain named variable placeholders for entire segments only. Each variable name must match a method parameter name. The method parameters must be of type String. For example: "file:///images/{category}/{file}" will match a resource request for file:///images/bicycles/tall_bike.jpg and pass bicycles as the category parameter and tall_bike.jpg as the file parameter.
      Default:
      ""

    • name

      String name
      Returns:
      A human-readable name for this resource. Clients can use this to populate UI elements, for example.

    • description

      String description
      Returns:
      A description of what this resource represents. Clients can use this to improve the LLM's understanding of available resources. It can be thought of as a "hint" to the model.
      Default:
      ""

    • mimeType

      String mimeType
      Returns:
      The MIME type of this resource. If not defined, String output will be presented as text/plain and byte arrays as appli
      Default:
      ""