write_resource

Instructions

Implementation Reference

• packages/server/src/resources/manager.ts:289-295 (handler)

  The write_resource tool handler callback that executes the write operation via resourceManager.write() and returns the result as JSON

    async ({ uri, operation }) => {
      const result = this.write(uri, operation);
      return {
        content: [{ type: 'text', text: JSON.stringify(result, null, 2) }],
      };
    }
  );

• packages/server/src/resources/manager.ts:173-208 (handler)

  Core write method that resolves URIs to file paths, applies operations, updates task timestamps, and handles file operations

  write(uri: string, operation: Operation): WriteResourceResult {
    try {
      const filePath = this.resolve(uri);
      const isTask = this.isTaskUri(uri);
      
      if (!existsSync(filePath)) {
        return {
          success: false,
          message: 'File not found',
          error: `Resource not found: ${uri} (${operation.type} requires existing file). Use backlog_create to create new entities.`,
        };
      }
  
      const fileContent = readFileSync(filePath, 'utf-8');
  
      let newContent = applyOperation(fileContent, operation);
      
      // Update timestamp for task files
      if (isTask) {
        newContent = this.updateTaskTimestamp(newContent);
      }
      
      writeFileSync(filePath, newContent, 'utf-8');
  
      return {
        success: true,
        message: `Successfully applied ${operation.type} to ${uri}`,
      };
    } catch (error) {
      return {
        success: false,
        message: 'Operation failed',
        error: error instanceof Error ? error.message : String(error),
      };
    }
  }

• packages/server/src/resources/manager.ts:265-287 (schema)

  Zod schema definition for write_resource tool input parameters, validating URI and operation types (str_replace, insert, append)

  inputSchema: z.object({
    uri: z.string().describe('MCP resource URI, e.g. mcp://backlog/path/to/file.md'),
    operation: z.preprocess(
      // Workaround: MCP clients stringify object params with $ref/oneOf schemas
      // https://github.com/anthropics/claude-code/issues/18260
      (val) => typeof val === 'string' ? JSON.parse(val) : val,
      z.discriminatedUnion('type', [
      z.object({
        type: z.literal('str_replace'),
        old_str: z.string().describe('String in file to replace (must match exactly)'),
        new_str: z.string().describe('New string to replace old_str with'),
      }),
      z.object({
        type: z.literal('insert'),
        insert_line: z.number().describe('Line number after which new_str will be inserted'),
        new_str: z.string().describe('String to insert'),
      }),
      z.object({
        type: z.literal('append'),
        new_str: z.string().describe('Content to append to the file'),
      }),
    ])).describe('Operation to apply'),
  }),

• packages/server/src/resources/manager.ts:255-296 (registration)

  Method that registers the write_resource tool with the MCP server, including description, input schema, and handler callback

   registerWriteTool(server: McpServer) {
     server.registerTool(
       'write_resource',
       {
         description: `Edit existing files on the MCP server. All file creation goes through backlog_create.
  * The \`append\` command will add content to the end of an existing file, automatically adding a newline if the file doesn't end with one.
  Notes for using the \`str_replace\` command:
  * The \`old_str\` parameter should match EXACTLY one or more consecutive lines from the original file. Be mindful of whitespaces!
  * If the \`old_str\` parameter is not unique in the file, the replacement will not be performed. Make sure to include enough context in \`old_str\` to make it unique
  * The \`new_str\` parameter should contain the edited lines that should replace the \`old_str\``,
         inputSchema: z.object({
           uri: z.string().describe('MCP resource URI, e.g. mcp://backlog/path/to/file.md'),
           operation: z.preprocess(
             // Workaround: MCP clients stringify object params with $ref/oneOf schemas
             // https://github.com/anthropics/claude-code/issues/18260
             (val) => typeof val === 'string' ? JSON.parse(val) : val,
             z.discriminatedUnion('type', [
             z.object({
               type: z.literal('str_replace'),
               old_str: z.string().describe('String in file to replace (must match exactly)'),
               new_str: z.string().describe('New string to replace old_str with'),
             }),
             z.object({
               type: z.literal('insert'),
               insert_line: z.number().describe('Line number after which new_str will be inserted'),
               new_str: z.string().describe('String to insert'),
             }),
             z.object({
               type: z.literal('append'),
               new_str: z.string().describe('Content to append to the file'),
             }),
           ])).describe('Operation to apply'),
         }),
       },
       async ({ uri, operation }) => {
         const result = this.write(uri, operation);
         return {
           content: [{ type: 'text', text: JSON.stringify(result, null, 2) }],
         };
       }
     );
   }

• packages/server/src/resources/operations.ts:5-41 (helper)

  Helper function that applies the actual text operations (str_replace, insert, append) to file content

  export function applyOperation(content: string, operation: Operation): string {
    switch (operation.type) {
      case 'str_replace': {
        const { old_str, new_str } = operation;
        if (!content.includes(old_str)) {
          throw new Error(`str_replace failed: old_str not found in content`);
        }
        // Check uniqueness - fail if old_str appears more than once
        const firstIndex = content.indexOf(old_str);
        const secondIndex = content.indexOf(old_str, firstIndex + 1);
        if (secondIndex !== -1) {
          throw new Error(`str_replace failed: old_str is not unique in file. Include more context to make it unique.`);
        }
        return content.replace(old_str, new_str);
      }
  
      case 'insert': {
        // insert_line: insert AFTER this line (1-based, like fs_write)
        const lines = content.split('\n');
        const lineNum = operation.insert_line;
        if (lineNum < 0 || lineNum > lines.length) {
          throw new Error(`insert failed: line ${lineNum} out of range (0-${lines.length})`);
        }
        lines.splice(lineNum, 0, operation.new_str);
        return lines.join('\n');
      }
  
      case 'append': {
        // Add newline if file doesn't end with one (like fs_write)
        const needsNewline = content.length > 0 && !content.endsWith('\n');
        return content + (needsNewline ? '\n' : '') + operation.new_str;
      }
  
      default:
        throw new Error(`Unknown operation type: ${(operation as any).type}`);
    }
  }