Class DefaultMcpClient

java.lang.Object
dev.langchain4j.mcp.client.DefaultMcpClient
All Implemented Interfaces:
McpClient, AutoCloseable
public class DefaultMcpClient extends Object implements McpClient

  • Constructor Details

  • Method Details

    • isModernProtocol

      public boolean isModernProtocol()

    • key

      public String key()
      Description copied from interface: McpClient
      Returns the unique key of this client.
      Specified by:
      key in interface McpClient

    • instructions

      public @Nullable String instructions()
      Description copied from interface: McpClient
      Returns the server instructions from the initialize result, or null if the server did not provide any.
      Specified by:
      instructions in interface McpClient

    • listTools

      public List<ToolSpecification> listTools()
      Description copied from interface: McpClient
      Obtains a list of tools from the MCP server.
      Specified by:
      listTools in interface McpClient

    • listTools

      public List<ToolSpecification> listTools(InvocationContext invocationContext)
      Description copied from interface: McpClient
      Obtains a list of tools from the MCP server.
      Specified by:
      listTools in interface McpClient

    • evictToolListCache

      public void evictToolListCache()
      Evicts the tool list cache, forcing the next call to listTools() to retrieve a fresh list of tools from the MCP server.

    • executeTool

      public ToolExecutionResult executeTool(ToolExecutionRequest executionRequest)
      Description copied from interface: McpClient
      Executes a tool on the MCP server and returns the result. Currently, this expects a tool execution to only contain text-based results or JSON structured content.
      Specified by:
      executeTool in interface McpClient

    • executeTool

      public ToolExecutionResult executeTool(ToolExecutionRequest executionRequest, InvocationContext invocationContext)
      Description copied from interface: McpClient
      Executes a tool on the MCP server and returns the result. Currently, this expects a tool execution to only contain text-based results or JSON structured content.
      Specified by:
      executeTool in interface McpClient

    • listResources

      public List<McpResource> listResources()
      Description copied from interface: McpClient
      Obtains the current list of resources available on the MCP server.
      Specified by:
      listResources in interface McpClient

    • listResources

      public List<McpResource> listResources(InvocationContext invocationContext)
      Description copied from interface: McpClient
      Obtains the current list of resources available on the MCP server.
      Specified by:
      listResources in interface McpClient

    • readResource

      public McpReadResourceResult readResource(String uri)
      Description copied from interface: McpClient
      Retrieves the contents of the resource with the specified URI. This also works for dynamic resources (templates).
      Specified by:
      readResource in interface McpClient

    • readResource

      public McpReadResourceResult readResource(String uri, InvocationContext invocationContext)
      Description copied from interface: McpClient
      Retrieves the contents of the resource with the specified URI. This also works for dynamic resources (templates).
      Specified by:
      readResource in interface McpClient

    • listPrompts

      public List<McpPrompt> listPrompts()
      Description copied from interface: McpClient
      Obtain a list of prompts available on the MCP server.
      Specified by:
      listPrompts in interface McpClient

    • getPrompt

      public McpGetPromptResult getPrompt(String name, Map<String,Object> arguments)
      Description copied from interface: McpClient
      Render the contents of a prompt.
      Specified by:
      getPrompt in interface McpClient

    • checkHealth

      public void checkHealth()
      Description copied from interface: McpClient
      Performs a health check that returns normally if the MCP server is reachable and properly responding to ping requests. If this method throws an exception, the health of this MCP client is considered degraded.
      Specified by:
      checkHealth in interface McpClient

    • setRoots

      public void setRoots(List<McpRoot> roots)
      Description copied from interface: McpClient
      Sets the roots that are made available to the server upon its request. After calling this method, the client also sends a notifications/roots/list_changed message to the server.
      Specified by:
      setRoots in interface McpClient

    • subscribeToResource

      public void subscribeToResource(String uri)
      Description copied from interface: McpClient
      Subscribes to updates for the resource with the specified URI. When the resource changes, the server will send a notifications/resources/updated notification. The client will invoke the onResourceUpdated callback (if configured) with the URI of the updated resource.
      Specified by:
      subscribeToResource in interface McpClient

    • unsubscribeFromResource

      public void unsubscribeFromResource(String uri)
      Description copied from interface: McpClient
      Unsubscribes from updates for the resource with the specified URI.
      Specified by:
      unsubscribeFromResource in interface McpClient

    • subscribeToResources

      public long subscribeToResources(List<String> uris)
      Description copied from interface: McpClient
      Subscribes to resource content update notifications for the given URIs. Once subscribed, the server notifies the client whenever one of those resources changes; the notifications are delivered to the callback registered via DefaultMcpClient.Builder#onResourceUpdated.

      The MCP specification requires the server to confirm a subscription before it sends anything on it, so this method blocks until that confirmation arrives and fails if it does not. When it returns normally, the subscription is established and the returned subscription ID can be passed to McpClient.unsubscribeFromResources(long) to stop receiving the notifications. How long the client waits for the confirmation is governed by DefaultMcpClient.Builder#resourcesTimeout(Duration).

      Because this method blocks, do not call it from inside a notification callback such as onResourceUpdated: those callbacks run on the thread that reads messages from the server, which is the same thread that would have to deliver the confirmation.

      Only available with MCP protocol version 2026-07-28 and later.

      Specified by:
      subscribeToResources in interface McpClient
      Parameters:
      uris - the list of resource URIs to subscribe to
      Returns:
      a subscription ID

    • unsubscribeFromResources

      public void unsubscribeFromResources(long subscriptionId)
      Description copied from interface: McpClient
      Unsubscribes from resource content update notifications for the given subscription ID. Only available with MCP protocol version 2026-07-28 and later.
      Specified by:
      unsubscribeFromResources in interface McpClient
      Parameters:
      subscriptionId - the subscription ID returned by McpClient.subscribeToResources(List)

    • listResourceTemplates

      public List<McpResourceTemplate> listResourceTemplates()
      Description copied from interface: McpClient
      Obtains the current list of resource templates (dynamic resources) available on the MCP server.
      Specified by:
      listResourceTemplates in interface McpClient

    • listResourceTemplates

      public List<McpResourceTemplate> listResourceTemplates(InvocationContext invocationContext)
      Description copied from interface: McpClient
      Obtains the current list of resource templates (dynamic resources) available on the MCP server.
      Specified by:
      listResourceTemplates in interface McpClient

    • close

      public void close()
      Specified by:
      close in interface AutoCloseable

    • builder

      public static DefaultMcpClient.Builder builder()