Instructions

Implementation Reference

• src/tools.ts:294-304 (handler)

  MCP tool handler for 'lookup_context'. Awaits parser instance, invokes parser.lookupContext with parameters, and returns JSON-formatted result as text content.
  handler: async ({ line, column, sourceMapUrl, contextLines }, getParser) => { const parser = await getParser(); const result = await parser.lookupContext(line, column, sourceMapUrl, contextLines); return { content: [{ type: "text", text: JSON.stringify(result, null, 2) }], } }
• src/tools.ts:280-293 (schema)

  Zod input schema for 'lookup_context' tool parameters: line (number), column (number), sourceMapUrl (string), contextLines (optional number, default 5).
  schema: { line: z.number({ description: "The line number in the compiled code (1-based)", }), column: z.number({ description: "The column number in the compiled code", }), sourceMapUrl: z.string({ description: "The URL of the source map file", }), contextLines: z.number({ description: "Number of context lines to include (default: 5)", }).optional().default(5), },
• src/tools.ts:263-305 (registration)

  Declarative tool definition object for 'lookup_context' in toolDefinitions array, used by registerTools to conditionally register the tool with the MCP server via server.tool().
  { name: "lookup_context", description: ` # Lookup Source Code Context This tool looks up original source code context for a specific line and column position in compiled/minified code. ## Parameters: - **line**: The line number in the compiled code (1-based) - **column**: The column number in the compiled code - **sourceMapUrl**: The URL of the source map file - **contextLines** (optional): Number of context lines to include before and after the target line (default: 5) ## Returns: - A JSON object containing the source code context snippet with file path, target line info, and surrounding context lines - Returns null if the position cannot be mapped `, schema: { line: z.number({ description: "The line number in the compiled code (1-based)", }), column: z.number({ description: "The column number in the compiled code", }), sourceMapUrl: z.string({ description: "The URL of the source map file", }), contextLines: z.number({ description: "Number of context lines to include (default: 5)", }).optional().default(5), }, handler: async ({ line, column, sourceMapUrl, contextLines }, getParser) => { const parser = await getParser(); const result = await parser.lookupContext(line, column, sourceMapUrl, contextLines); return { content: [{ type: "text", text: JSON.stringify(result, null, 2) }], } } },
• src/parser.ts:393-408 (helper)

  Core helper method in Parser class: lookupContext. Validates URL, fetches source map content, initializes parser, calls external sourceMapParser.lookup_context WASM function, and returns the source context result. Invoked by the tool handler.
  public async lookupContext(line: number, column: number, sourceMapUrl: string, contextLines: number = 5) { validateUrl(sourceMapUrl); await this.init(); try { const sourceMapContent = await this.fetchSourceMapContent(sourceMapUrl); // Use the high-level lookup_context function directly const result = sourceMapParser.lookup_context(sourceMapContent, line, column, contextLines); return result; } catch (error) { throw new Error("lookup context error: " + (error instanceof Error ? error.message : error), { cause: error, }); } }