Tree-Hugger-JS MCP Server

Instructions

Implementation Reference

• src/index.ts:518-567 (handler)

  The handler function that executes the 'find_pattern' tool. It checks if AST is loaded, uses tree.find(pattern) to locate the first matching node, extracts metadata, and returns formatted node information or error.

  private async findPattern(args: { pattern: string }) {
    if (!this.currentAST) {
      return {
        content: [{
          type: "text",
          text: "No AST loaded. Please use parse_code first.",
        }],
        isError: true,
      };
    }
  
    try {
      const result = this.currentAST.tree.find(args.pattern);
      
      if (!result) {
        return {
          content: [{
            type: "text",
            text: `No match found for pattern: ${args.pattern}`,
          }],
        };
      }
  
      const nodeInfo = {
        type: result.type,
        text: result.text.length > 200 ? result.text.slice(0, 200) + '...' : result.text,
        line: result.line,
        column: result.column,
        name: result.name,
        startPosition: result.startPosition,
        endPosition: result.endPosition,
        childrenCount: result.children.length,
      };
  
      return {
        content: [{
          type: "text", 
          text: `Found match for pattern "${args.pattern}":\n${JSON.stringify(nodeInfo, null, 2)}`,
        }],
      };
    } catch (error) {
      return {
        content: [{
          type: "text",
          text: `Error finding pattern: ${error instanceof Error ? error.message : String(error)}`,
        }],
        isError: true,
      };
    }
  }

• src/index.ts:205-214 (schema)

  Input schema definition for the 'find_pattern' tool, specifying a required 'pattern' string parameter.

  inputSchema: {
    type: "object",
    properties: {
      pattern: {
        type: "string",
        description: "Pattern using intuitive syntax: 'function', 'class[name=\"MyClass\"]', 'function[async]', 'call[text*=\"fetch\"]'"
      }
    },
    required: ["pattern"],
  },

• src/index.ts:416-417 (registration)

  Registration in the CallToolRequestSchema switch statement that dispatches to the findPattern handler.

  case "find_pattern":
    return await this.findPattern(args as { pattern: string });

• src/index.ts:202-215 (registration)

  Tool registration in the ListToolsRequestSchema handler, including name, description, and input schema.

  {
    name: "find_pattern",
    description: "Find first node matching the specified pattern using tree-hugger-js intuitive syntax. Use for targeted searches when you need one specific match.\n\nExamples:\n• Find main function: find_pattern('function[name=\"main\"]')\n• Find React component: find_pattern('function[name=\"UserProfile\"]')\n• Find async functions: find_pattern('function[async]')\n• Find specific class: find_pattern('class[name=\"UserManager\"]')\n• Find error handling: find_pattern('call[text*=\"catch\"]')\n• Find JSX with props: find_pattern('jsx:has(jsx-attribute[name=\"className\"])')\n• Debug specific calls: find_pattern('call[text*=\"console.log\"]')",
    inputSchema: {
      type: "object",
      properties: {
        pattern: {
          type: "string",
          description: "Pattern using intuitive syntax: 'function', 'class[name=\"MyClass\"]', 'function[async]', 'call[text*=\"fetch\"]'"
        }
      },
      required: ["pattern"],
    },
  },