language-server-mcp

Instructions

Implementation Reference

• src/index.ts:421-479 (handler)

  The main handler function for the 'get_hover' tool. It creates or retrieves a language server instance, opens the provided document, sends a hover request at the specified position, and returns the hover contents or an error.

  private async handleGetHover(args: any): Promise<any> {
    const { languageId, filePath, content, line, character, projectRoot } = args;
    console.log(`[handleGetHover] Processing request for ${languageId}`);
    
    const server = await this.getOrCreateServer(languageId, projectRoot);
    const actualRoot = server.workspaceRoot;
  
    const absolutePath = isAbsolute(filePath) ? filePath : join(actualRoot, filePath);
    const uri = `file://${absolutePath}`;
  
    // Ensure directory exists (for languages that may require file presence)
    const dir = dirname(absolutePath);
    if (!existsSync(dir)) {
      mkdirSync(dir, { recursive: true });
    }
  
    const textDocument: TextDocumentItem = {
      uri,
      languageId,
      version: 1,
      text: content,
    };
  
    console.log(`[handleGetHover] Sending document to server:`, textDocument);
    await server.connection.sendNotification('textDocument/didOpen', {
      textDocument,
    } as DidOpenTextDocumentParams);
  
    try {
      console.log(`[handleGetHover] Requesting hover information`);
      const hover: Hover = await server.connection.sendRequest('textDocument/hover', {
        textDocument: { uri } as TextDocumentIdentifier,
        position: { line, character },
      });
  
      console.log(`[handleGetHover] Received hover response:`, hover);
      return {
        content: [
          {
            type: 'text',
            text: hover?.contents
              ? JSON.stringify(hover.contents, null, 2)
              : 'No hover information available',
          },
        ],
      };
    } catch (error) {
      console.error('[handleGetHover] Request failed:', error);
      return {
        content: [
          {
            type: 'text',
            text: 'Failed to get hover information',
          },
        ],
        isError: true,
      };
    }
  }

• src/index.ts:295-323 (schema)

  Input schema definition for the 'get_hover' tool, specifying parameters like languageId, filePath, content, position (line, character), and projectRoot.

    type: 'object',
    properties: {
      languageId: { 
        type: 'string',
        description: 'The language identifier (e.g., "typescript", "javascript")'
      },
      filePath: { 
        type: 'string',
        description: 'Absolute or relative path to the source file'
      },
      content: { 
        type: 'string',
        description: 'The current content of the file'
      },
      line: { 
        type: 'number',
        description: 'Zero-based line number for hover position'
      },
      character: { 
        type: 'number',
        description: 'Zero-based character offset for hover position'
      },
      projectRoot: { 
        type: 'string',
        description: 'Important: Root directory of the project for resolving imports and node_modules where the tsconfig.json or jsconfig.json is located'
      },
    },
    required: ['languageId', 'filePath', 'content', 'line', 'character', 'projectRoot'],
  },

• src/index.ts:291-324 (registration)

  Registration of the 'get_hover' tool in the MCP server's tool list, returned by ListToolsRequestSchema handler.

  {
    name: 'get_hover',
    description: 'Get hover information for a position in a document',
    inputSchema: {
      type: 'object',
      properties: {
        languageId: { 
          type: 'string',
          description: 'The language identifier (e.g., "typescript", "javascript")'
        },
        filePath: { 
          type: 'string',
          description: 'Absolute or relative path to the source file'
        },
        content: { 
          type: 'string',
          description: 'The current content of the file'
        },
        line: { 
          type: 'number',
          description: 'Zero-based line number for hover position'
        },
        character: { 
          type: 'number',
          description: 'Zero-based character offset for hover position'
        },
        projectRoot: { 
          type: 'string',
          description: 'Important: Root directory of the project for resolving imports and node_modules where the tsconfig.json or jsconfig.json is located'
        },
      },
      required: ['languageId', 'filePath', 'content', 'line', 'character', 'projectRoot'],
    },
  },

• src/index.ts:395-396 (registration)

  Dispatch case in the CallToolRequestSchema handler that routes 'get_hover' calls to the handleGetHover method.

  case 'get_hover':
    result = await this.handleGetHover(args);