Package io.modelcontextprotocol.server

Class McpSyncServer

java.lang.Object
io.modelcontextprotocol.server.McpSyncServer
public class McpSyncServer extends Object
A synchronous implementation of the Model Context Protocol (MCP) server that wraps McpAsyncServer to provide blocking operations. This class delegates all operations to an underlying async server instance while providing a simpler, synchronous API for scenarios where reactive programming is not required.

The MCP server enables AI models to expose tools, resources, and prompts through a standardized interface. Key features available through this synchronous API include:

  • Tool registration and management for extending AI model capabilities
  • Resource handling with URI-based addressing for providing context
  • Prompt template management for standardized interactions
  • Real-time client notifications for state changes
  • Structured logging with configurable severity levels
  • Support for client-side AI model sampling

While McpAsyncServer uses Project Reactor's Mono and Flux types for non-blocking operations, this class converts those into blocking calls, making it more suitable for:

  • Traditional synchronous applications
  • Simple scripting scenarios
  • Testing and debugging
  • Cases where reactive programming adds unnecessary complexity

The server supports runtime modification of its capabilities through methods like addTool(io.modelcontextprotocol.server.McpServerFeatures.SyncToolSpecification), addResource(io.modelcontextprotocol.server.McpServerFeatures.SyncResourceSpecification), and addPrompt(io.modelcontextprotocol.server.McpServerFeatures.SyncPromptSpecification), automatically notifying connected clients of changes when configured to do so.

Author:
Christian Tzolov, Dariusz Jędrzejczyk
See Also:

  • Constructor Details

    • McpSyncServer

      public McpSyncServer(McpAsyncServer asyncServer)
      Creates a new synchronous server that wraps the provided async server.
      Parameters:
      asyncServer - The async server to wrap

    • McpSyncServer

      public McpSyncServer(McpAsyncServer asyncServer, boolean immediateExecution)
      Creates a new synchronous server that wraps the provided async server.
      Parameters:
      asyncServer - The async server to wrap
      immediateExecution - Tools, prompts, and resources handlers execute work without blocking code offloading. Do NOT set to true if the asyncServer's transport is non-blocking.

  • Method Details

    • addTool

      public void addTool(McpServerFeatures.SyncToolSpecification toolHandler)
      Add a new tool handler.
      Parameters:
      toolHandler - The tool handler to add

    • listTools

      public List<McpSchema.Tool> listTools()
      List all registered tools.
      Returns:
      A list of all registered tools

    • removeTool

      public void removeTool(String toolName)
      Remove a tool handler.
      Parameters:
      toolName - The name of the tool handler to remove

    • addResource

      public void addResource(McpServerFeatures.SyncResourceSpecification resourceSpecification)
      Add a new resource handler.
      Parameters:
      resourceSpecification - The resource specification to add

    • listResources

      public List<McpSchema.Resource> listResources()
      List all registered resources.
      Returns:
      A list of all registered resources

    • removeResource

      public void removeResource(String resourceUri)
      Remove a resource handler.
      Parameters:
      resourceUri - The URI of the resource handler to remove

    • addResourceTemplate

      public void addResourceTemplate(McpServerFeatures.SyncResourceTemplateSpecification resourceTemplateSpecification)
      Add a new resource template.
      Parameters:
      resourceTemplateSpecification - The resource template specification to add

    • listResourceTemplates

      public List<McpSchema.ResourceTemplate> listResourceTemplates()
      List all registered resource templates.
      Returns:
      A list of all registered resource templates

    • removeResourceTemplate

      public void removeResourceTemplate(String uriTemplate)
      Remove a resource template.
      Parameters:
      uriTemplate - The URI template of the resource template to remove

    • addPrompt

      public void addPrompt(McpServerFeatures.SyncPromptSpecification promptSpecification)
      Add a new prompt handler.
      Parameters:
      promptSpecification - The prompt specification to add

    • listPrompts

      public List<McpSchema.Prompt> listPrompts()
      List all registered prompts.
      Returns:
      A list of all registered prompts

    • removePrompt

      public void removePrompt(String promptName)
      Remove a prompt handler.
      Parameters:
      promptName - The name of the prompt handler to remove

    • notifyToolsListChanged

      public void notifyToolsListChanged()
      Notify clients that the list of available tools has changed.

    • getServerCapabilities

      public McpSchema.ServerCapabilities getServerCapabilities()
      Get the server capabilities that define the supported features and functionality.
      Returns:
      The server capabilities

    • getServerInfo

      public McpSchema.Implementation getServerInfo()
      Get the server implementation information.
      Returns:
      The server implementation details

    • notifyResourcesListChanged

      public void notifyResourcesListChanged()
      Notify clients that the list of available resources has changed.

    • notifyResourcesUpdated

      public void notifyResourcesUpdated(McpSchema.ResourcesUpdatedNotification resourcesUpdatedNotification)
      Notify clients that the resources have updated.

    • notifyPromptsListChanged

      public void notifyPromptsListChanged()
      Notify clients that the list of available prompts has changed.

    • closeGracefully

      public void closeGracefully()
      Close the server gracefully.

    • close

      public void close()
      Close the server immediately.

    • getAsyncServer

      public McpAsyncServer getAsyncServer()
      Get the underlying async server instance.
      Returns:
      The wrapped async server