read_file
Read file contents from the filesystem, handling large files through chunked reading with line-based pagination for efficient processing.
Instructions
Read file contents. For large files (>500 lines), use start_line to read in chunks (e.g., 0, 500, 1000). Each call returns up to 500 lines. Binary files return metadata only.
Input Schema
TableJSON Schema
| Name | Required | Description | Default |
|---|---|---|---|
| path | Yes | File path to read | |
| start_line | No | Line number to start reading from (0-indexed). For large files, read in chunks: start_line=0 (first 500), start_line=500 (next 500), etc. |
Implementation Reference
- index.ts:283-338 (handler)Main handler for the 'read_file' tool. Handles input validation with Zod, path validation, binary file detection, file reading via helper, pagination logic, and formats the response as MCP content.
case 'read_file': { const schema = z.object({ path: z.string(), start_line: z.number().optional().default(0) }); const { path, start_line } = schema.parse(args); const validatedPath = await validatePath(path); // Check if binary const isBinary = await isBinaryFile(validatedPath); if (isBinary) { const stats = await getFileStats(validatedPath); return { content: [{ type: 'text', text: JSON.stringify({ path: validatedPath, error: 'Binary file', message: 'This appears to be a binary file. Use get_file_info for metadata.', size: stats.size, type: 'binary' }, null, 2) }] }; } // Read file content const content = await readFileContent(validatedPath); const totalLines = countLines(content); // Check if pagination is needed if (shouldPaginate(totalLines) || start_line > 0) { const result = paginateFileContent(validatedPath, content, start_line, LINES_PER_CHUNK); return { content: [{ type: 'text', text: JSON.stringify(result, null, 2) }] }; } // Return full file return { content: [{ type: 'text', text: JSON.stringify({ path: validatedPath, content, startLine: 0, endLine: totalLines - 1, totalLines, hasMore: false }, null, 2) }] }; } - index.ts:78-96 (schema)MCP tool definition for 'read_file' including name, description, and JSON schema for input parameters (path and optional start_line). This schema is returned by ListTools.
{ name: 'read_file', description: 'Read file contents. For large files (>500 lines), use start_line to read in chunks (e.g., 0, 500, 1000). Each call returns up to 500 lines. Binary files return metadata only.', inputSchema: { type: 'object', properties: { path: { type: 'string', description: 'File path to read' }, start_line: { type: 'number', description: 'Line number to start reading from (0-indexed). For large files, read in chunks: start_line=0 (first 500), start_line=500 (next 500), etc.', default: 0 } }, required: ['path'] } }, - index.ts:260-262 (registration)Registration of the ListTools handler which returns the static tools array containing the 'read_file' tool definition.
server.setRequestHandler(ListToolsRequestSchema, async () => ({ tools })); - lib.ts:103-105 (helper)Core helper function that performs the actual file reading using Node.js fs.readFile. Called by the read_file handler.
export async function readFileContent(filePath: string, encoding: string = 'utf-8'): Promise<string> { return await fs.readFile(filePath, encoding as BufferEncoding); }