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/**
* @license
* Copyright 2025 Google LLC
* SPDX-License-Identifier: Apache-2.0
*/
import {
Config,
getErrorMessage,
getMCPServerPrompts,
} from '@google/gemini-cli-core';
import {
CommandContext,
CommandKind,
SlashCommand,
SlashCommandActionReturn,
} from '../ui/commands/types.js';
import { ICommandLoader } from './types.js';
import { PromptArgument } from '@modelcontextprotocol/sdk/types.js';
/**
* Discovers and loads executable slash commands from prompts exposed by
* Model-Context-Protocol (MCP) servers.
*/
export class McpPromptLoader implements ICommandLoader {
constructor(private readonly config: Config | null) {}
/**
* Loads all available prompts from all configured MCP servers and adapts
* them into executable SlashCommand objects.
*
* @param _signal An AbortSignal (unused for this synchronous loader).
* @returns A promise that resolves to an array of loaded SlashCommands.
*/
loadCommands(_signal: AbortSignal): Promise<SlashCommand[]> {
const promptCommands: SlashCommand[] = [];
if (!this.config) {
return Promise.resolve([]);
}
const mcpServers = this.config.getMcpServers() || {};
for (const serverName in mcpServers) {
const prompts = getMCPServerPrompts(this.config, serverName) || [];
for (const prompt of prompts) {
const commandName = `${prompt.name}`;
const newPromptCommand: SlashCommand = {
name: commandName,
description: prompt.description || `Invoke prompt ${prompt.name}`,
kind: CommandKind.MCP_PROMPT,
subCommands: [
{
name: 'help',
description: 'Show help for this prompt',
kind: CommandKind.MCP_PROMPT,
action: async (): Promise<SlashCommandActionReturn> => {
if (!prompt.arguments || prompt.arguments.length === 0) {
return {
type: 'message',
messageType: 'info',
content: `Prompt "${prompt.name}" has no arguments.`,
};
}
let helpMessage = `Arguments for "${prompt.name}":\n\n`;
if (prompt.arguments && prompt.arguments.length > 0) {
helpMessage += `You can provide arguments by name (e.g., --argName="value") or by position.\n\n`;
helpMessage += `e.g., ${prompt.name} ${prompt.arguments?.map((_) => `"foo"`)} is equivalent to ${prompt.name} ${prompt.arguments?.map((arg) => `--${arg.name}="foo"`)}\n\n`;
}
for (const arg of prompt.arguments) {
helpMessage += ` --${arg.name}\n`;
if (arg.description) {
helpMessage += ` ${arg.description}\n`;
}
helpMessage += ` (required: ${
arg.required ? 'yes' : 'no'
})\n\n`;
}
return {
type: 'message',
messageType: 'info',
content: helpMessage,
};
},
},
],
action: async (
context: CommandContext,
args: string,
): Promise<SlashCommandActionReturn> => {
if (!this.config) {
return {
type: 'message',
messageType: 'error',
content: 'Config not loaded.',
};
}
const promptInputs = this.parseArgs(args, prompt.arguments);
if (promptInputs instanceof Error) {
return {
type: 'message',
messageType: 'error',
content: promptInputs.message,
};
}
try {
const mcpServers = this.config.getMcpServers() || {};
const mcpServerConfig = mcpServers[serverName];
if (!mcpServerConfig) {
return {
type: 'message',
messageType: 'error',
content: `MCP server config not found for '${serverName}'.`,
};
}
const result = await prompt.invoke(promptInputs);
if (result['error']) {
return {
type: 'message',
messageType: 'error',
content: `Error invoking prompt: ${result['error']}`,
};
}
if (!result.messages?.[0]?.content?.['text']) {
return {
type: 'message',
messageType: 'error',
content:
'Received an empty or invalid prompt response from the server.',
};
}
return {
type: 'submit_prompt',
content: JSON.stringify(result.messages[0].content.text),
};
} catch (error) {
return {
type: 'message',
messageType: 'error',
content: `Error: ${getErrorMessage(error)}`,
};
}
},
completion: async (_: CommandContext, partialArg: string) => {
if (!prompt || !prompt.arguments) {
return [];
}
const suggestions: string[] = [];
const usedArgNames = new Set(
(partialArg.match(/--([^=]+)/g) || []).map((s) => s.substring(2)),
);
for (const arg of prompt.arguments) {
if (!usedArgNames.has(arg.name)) {
suggestions.push(`--${arg.name}=""`);
}
}
return suggestions;
},
};
promptCommands.push(newPromptCommand);
}
}
return Promise.resolve(promptCommands);
}
private parseArgs(
userArgs: string,
promptArgs: PromptArgument[] | undefined,
): Record<string, unknown> | Error {
const argValues: { [key: string]: string } = {};
const promptInputs: Record<string, unknown> = {};
// arg parsing: --key="value" or --key=value
const namedArgRegex = /--([^=]+)=(?:"((?:\\.|[^"\\])*)"|([^ ]*))/g;
let match;
const remainingArgs: string[] = [];
let lastIndex = 0;
while ((match = namedArgRegex.exec(userArgs)) !== null) {
const key = match[1];
const value = match[2] ?? match[3]; // Quoted or unquoted value
argValues[key] = value;
// Capture text between matches as potential positional args
if (match.index > lastIndex) {
remainingArgs.push(userArgs.substring(lastIndex, match.index).trim());
}
lastIndex = namedArgRegex.lastIndex;
}
// Capture any remaining text after the last named arg
if (lastIndex < userArgs.length) {
remainingArgs.push(userArgs.substring(lastIndex).trim());
}
const positionalArgs = remainingArgs.join(' ').split(/ +/);
if (!promptArgs) {
return promptInputs;
}
for (const arg of promptArgs) {
if (argValues[arg.name]) {
promptInputs[arg.name] = argValues[arg.name];
}
}
const unfilledArgs = promptArgs.filter(
(arg) => arg.required && !promptInputs[arg.name],
);
const missingArgs: string[] = [];
for (let i = 0; i < unfilledArgs.length; i++) {
if (positionalArgs.length > i && positionalArgs[i]) {
promptInputs[unfilledArgs[i].name] = positionalArgs[i];
} else {
missingArgs.push(unfilledArgs[i].name);
}
}
if (missingArgs.length > 0) {
const missingArgNames = missingArgs.map((name) => `--${name}`).join(', ');
return new Error(`Missing required argument(s): ${missingArgNames}`);
}
return promptInputs;
}
}
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