@lobehub/chat/src/server/services/mcp/index.ts

Lobe Chat - an open-source, high-performance chatbot framework that supports speech synthesis, multimodal, and extensible Function Call plugin system. Supports one-click free deployment of your private ChatGPT/LLM web application.

import { LobeChatPluginApi, LobeChatPluginManifest, PluginSchema } from '@lobehub/chat-plugin-sdk';
import { McpError } from '@modelcontextprotocol/sdk/types.js';
import { TRPCError } from '@trpc/server';
import debug from 'debug';

import { MCPClient, MCPClientParams, StdioMCPParams } from '@/libs/mcp';
import { CustomPluginMetadata } from '@/types/tool/plugin';
import { safeParseJSON } from '@/utils/safeParseJSON';

const log = debug('lobe-mcp:service');

class MCPService {
  // --- MCP Interaction ---

  // listTools now accepts MCPClientParams
  async listTools(params: MCPClientParams): Promise<LobeChatPluginApi[]> {
    const client = await this.getClient(params); // Get client using params
    log(`Listing tools using client for params: %O`, params);

    try {
      const result = await client.listTools();
      log(`Tools listed successfully for params: %O, result count: %d`, params, result.length);
      return result.map<LobeChatPluginApi>((item) => ({
        // Assuming identifier is the unique name/id
        description: item.description,
        name: item.name,
        parameters: item.inputSchema as PluginSchema,
      }));
    } catch (error) {
      console.error(`Error listing tools for params %O:`, params, error);
      // Propagate a TRPCError for better handling upstream
      throw new TRPCError({
        cause: error,
        code: 'INTERNAL_SERVER_ERROR',
        message: `Error listing tools from MCP server: ${(error as Error).message}`,
      });
    }
  }

  // callTool now accepts MCPClientParams, toolName, and args
  async callTool(params: MCPClientParams, toolName: string, argsStr: any): Promise<any> {
    const client = await this.getClient(params); // Get client using params

    const args = safeParseJSON(argsStr);

    log(`Calling tool "${toolName}" using client for params: %O with args: %O`, params, args);

    try {
      // Delegate the call to the MCPClient instance
      const result = await client.callTool(toolName, args); // Pass args directly
      log(`Tool "${toolName}" called successfully for params: %O, result: %O`, params, result);
      const { content, isError } = result;

      if (isError) return result;

      const data = content as { text: string; type: 'text' }[];

      const text = data?.[0]?.text;

      if (!text) return data;

      // try to get json object, which will be stringify in the client
      const json = safeParseJSON(text);
      if (json) return json;

      return text;
    } catch (error) {
      if (error instanceof McpError) {
        const mcpError = error as McpError;

        return mcpError.message;
      }

      console.error(`Error calling tool "${toolName}" for params %O:`, params, error);
      // Propagate a TRPCError
      throw new TRPCError({
        cause: error,
        code: 'INTERNAL_SERVER_ERROR',
        message: `Error calling tool "${toolName}" on MCP server: ${(error as Error).message}`,
      });
    }
  }

  // TODO: Consider adding methods for managing the client lifecycle if needed,
  // e.g., explicitly closing clients on shutdown or after inactivity,
  // although for serverless, on-demand creation/retrieval might be sufficient.

  // TODO: Implement methods like listResources, getResource, listPrompts, getPrompt if needed,
  // following the pattern of accepting MCPClientParams.

  // --- Client Management (Replaces Connection Management) ---

  // Private method to get or initialize a client based on parameters
  private async getClient(params: MCPClientParams): Promise<MCPClient> {
    try {
      // Ensure stdio is only attempted in desktop/server environments within the client itself
      // or add a check here if MCPClient doesn't handle it.
      // Example check (adjust based on where environment check is best handled):
      // if (params.type === 'stdio' && typeof window !== 'undefined') {
      //   throw new Error('Stdio MCP type is not supported in browser environment.');
      // }

      const client = new MCPClient(params);
      await client.initialize({
        onProgress: (progress) => {
          log(`New client initializing... ${progress.progress}/${progress.total}`);
        },
      }); // Initialization logic should be within MCPClient
      log(`New client initialized`);
      return client;
    } catch (error) {
      console.error(`Failed to initialize MCP client`, error);
      // Do not cache failed initializations
      throw new TRPCError({
        cause: error,
        code: 'INTERNAL_SERVER_ERROR',
        message: `Failed to initialize MCP client, reason: ${(error as Error).message}`,
      });
    }
  }

  async getStreamableMcpServerManifest(
    identifier: string,
    url: string,
    metadata?: CustomPluginMetadata,
  ): Promise<LobeChatPluginManifest> {
    const tools = await this.listTools({ name: identifier, type: 'http', url }); // Get client using params

    return {
      api: tools,
      identifier,
      meta: {
        avatar: metadata?.avatar || 'MCP_AVATAR',
        description:
          metadata?.description ||
          `${identifier} MCP server has ${tools.length} tools, like "${tools[0]?.name}"`,
        title: identifier,
      },
      // TODO: temporary
      type: 'mcp' as any,
    };
  }

  async getStdioMcpServerManifest(
    params: Omit<StdioMCPParams, 'type'>,
    metadata?: CustomPluginMetadata,
  ): Promise<LobeChatPluginManifest> {
    const tools = await this.listTools({
      args: params.args,
      command: params.command,
      env: params.env,
      name: params.name,
      type: 'stdio',
    });

    const identifier = params.name;
    return {
      api: tools,
      identifier,
      meta: {
        avatar: metadata?.avatar || 'MCP_AVATAR',
        description:
          metadata?.description ||
          `${identifier} MCP server has ${tools.length} tools, like "${tools[0]?.name}"`,
        title: identifier,
      },
      // TODO: temporary
      type: 'mcp' as any,
    };
  }
}

// Export a singleton instance
export const mcpService = new MCPService();