viyan-mcp: Skill for Claude Code

When to Use

Use this skill when implementing request validation, authorization checks, response mapping, logging, error handling, or performance tracking on NitroStack tool methods.

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1. Guards (Guard and @UseGuards)

Guards determine if a request should be processed by a tool handler based on authentication, authorization, or other conditions.

Interface:

import { Guard, ExecutionContext } from '@nitrostack/core';

export interface Guard {
  canActivate(context: ExecutionContext): boolean | Promise<boolean>;
}

Example:

import { Guard, ExecutionContext, Injectable } from '@nitrostack/core';

@Injectable()
export class RolesGuard implements Guard {
  async canActivate(context: ExecutionContext): Promise<boolean> {
    const userRoles = context.clientMetadata?.roles || [];
    return userRoles.includes('admin');
  }
}

Apply the guard using @UseGuards(...):

import { Tool, UseGuards, z } from '@nitrostack/core';
import { RolesGuard } from './roles.guard.js';

export class AdminTools {
  @Tool({
    name: 'delete_system_logs',
    description: 'Delete all system logs from the server.',
    inputSchema: z.object({}),
  })
  @UseGuards(RolesGuard)
  async deleteLogs() {
    return { success: true };
  }
}

---

2. Interceptors (InterceptorInterface and @UseInterceptors)

Interceptors can transform/intercept input arguments or mapped output from a tool method execution.

Interface:

import { ExecutionContext } from '@nitrostack/core';

export interface InterceptorInterface {
  intercept(context: ExecutionContext, next: () => Promise<unknown>): Promise<unknown>;
}

Example:

import { InterceptorInterface, ExecutionContext, Injectable } from '@nitrostack/core';

@Injectable()
export class TimingInterceptor implements InterceptorInterface {
  async intercept(context: ExecutionContext, next: () => Promise<unknown>): Promise<unknown> {
    const start = Date.now();
    const result = await next();
    const duration = Date.now() - start;
    context.logger.info(`Execution took ${duration}ms`);
    return {
      ...result,
      _meta: { durationMs: duration }
    };
  }
}