MCP Playground Server

Instructions

Implementation Reference

• src/index.ts:138-151 (handler)

  MCP tool handler that extracts the command argument, calls the suggester's validateCommand method, and formats the result as MCP content response.
  private async handleCommandValidate(args: any) { const { command } = args; const validation = await this.suggester.validateCommand(command); return { content: [ { type: "text", text: JSON.stringify(validation, null, 2), }, ], }; }
• src/suggester.ts:159-247 (helper)

  Core implementation of command validation: parses command parts, validates against command structure from parser, checks for unknown commands/options, required options, provides suggestions and errors.
  async validateCommand(command: string): Promise<ValidationResult> { const result: ValidationResult = { valid: true, errors: [], warnings: [], suggestions: [] }; const parts = command.trim().split(' ').filter(p => p.length > 0); if (parts.length === 0) { result.valid = false; result.errors.push('Empty command'); return result; } // Check if starts with 'playground' if (parts[0] !== 'playground') { result.valid = false; result.errors.push('Command must start with "playground"'); return result; } const commandParts = parts.slice(1).filter(part => !part.startsWith('--')); const optionParts = parts.slice(1).filter(part => part.startsWith('--')); // Validate command path if (commandParts.length === 0) { result.valid = false; result.errors.push('No command specified'); return result; } const foundCommand = this.parser.findCommand(commandParts); if (!foundCommand) { result.valid = false; result.errors.push(`Unknown command: ${commandParts.join(' ')}`); // Suggest similar commands const suggestions = await this.getSuggestions(commandParts.join(' ')); result.suggestions = suggestions.slice(0, 3).map(s => s.completion); return result; } // Validate options const providedOptions = new Set<string>(); for (let i = 0; i < optionParts.length; i++) { const optionPart = optionParts[i]; const optionName = optionPart.replace(/^--?/, ''); const option = foundCommand.options?.find(opt => opt.name === optionName); if (!option) { result.valid = false; result.errors.push(`Unknown option: ${optionPart}`); continue; } if (providedOptions.has(optionName) && !option.repeatable) { result.warnings.push(`Option --${optionName} specified multiple times but is not repeatable`); } providedOptions.add(optionName); } // Check required options foundCommand.options?.forEach(option => { if (option.required && !providedOptions.has(option.name)) { result.valid = false; result.errors.push(`Missing required option: --${option.name}`); } }); // Check if command needs subcommands if (foundCommand.subcommands && foundCommand.subcommands.length > 0) { // Check if this is a terminal command or needs subcommands const hasSubcommand = commandParts.length > 1; if (!hasSubcommand) { result.warnings.push('This command has subcommands available'); result.suggestions.push( ...foundCommand.subcommands.slice(0, 3).map(sub => `playground ${commandParts.join(' ')} ${sub.name}` ) ); } } return result; }
• src/index.ts:59-72 (registration)

  Tool registration in the ListToolsRequestSchema handler, defining name, description, and input schema.
  { name: "playground_command_validate", description: "Validate a complete playground command and suggest corrections", inputSchema: { type: "object", properties: { command: { type: "string", description: "Complete playground command to validate", }, }, required: ["command"], }, },
• src/index.ts:62-71 (schema)

  Input schema definition for the playground_command_validate tool.
  inputSchema: { type: "object", properties: { command: { type: "string", description: "Complete playground command to validate", }, }, required: ["command"], },