Converting APIs to MCPs

// Your database already has summaries
const results = await db.query(`
  SELECT id, title, summary_slug, key_metrics 
  FROM articles 
  WHERE topic = ?
  LIMIT 5
`, [input.topic]);

// Return only the pre-computed summary fields
return results.map(r => ({
  id: r.id,
  title: r.title,
  summary: r.summary_slug  // Already computed, stored in DB
}));

import OpenAI from 'openai';

const openai = new OpenAI();

@Tool({ description: "Search articles and return summaries" })
async searchArticles(input: { query: string }) {
  // Fetch from your API
  const rawResults = await api.search(input.query);
  
  // Summarize each result with a fast, cheap model
  const summaries = await Promise.all(
    rawResults.slice(0, 5).map(async (item) => {
      const summary = await openai.chat.completions.create({
        model: "gpt-5.2",  // Fast, cheap nano model
        messages: [{
          role: "user",
          content: `Summarize in 2 sentences: ${item.content.slice(0, 2000)}`
        }],
        max_tokens: 100
      });
      
      return {
        id: item.id,
        title: item.title,
        summary: summary.choices[0].message.content
      };
    })
  );
  
  return summaries;
}

import { Service, Tool } from 'leanmcp';
import { OAuth, Protected, AuthUser } from '@leanmcp/auth';

@Service()
@OAuth({
  provider: 'custom',
  clientId: process.env.OAUTH_CLIENT_ID,
  clientSecret: process.env.OAUTH_CLIENT_SECRET,
  authorizationUrl: 'https://your-auth-server.com/authorize',
  tokenUrl: 'https://your-auth-server.com/token',
  scopes: ['read:articles', 'write:comments']
})
export class ArticleService {
  
  @Tool({ description: "Get user's saved articles" })
  @Protected()
  async getSavedArticles(@AuthUser() user: any) {
    // User is authenticated with your existing OAuth
    // Same token that works with your web app
    return await api.getArticles({ userId: user.sub });
  }
}

// Don't request all scopes
scopes: ['read', 'write', 'delete', 'admin']  // ❌ Too broad

// Request only what's needed
scopes: ['read:articles', 'read:profile']  // ✅ Minimal

import { Service, Tool } from 'leanmcp';
import { OAuth, Protected, AuthUser } from '@leanmcp/auth';

@Service()
@OAuth({
  provider: 'custom',
  clientId: process.env.HUBSPOT_CLIENT_ID,
  clientSecret: process.env.HUBSPOT_CLIENT_SECRET,
  authorizationUrl: 'https://app.hubspot.com/oauth/authorize',
  tokenUrl: 'https://api.hubapi.com/oauth/v1/token',
  scopes: ['crm.objects.contacts.read']
})
export class HubSpotMCP {
  
  @Tool({ description: "Search contacts" })
  @Protected()
  async searchContacts(
    @AuthUser() user: any,
    input: { query: string }
  ) {
    // Fetch from HubSpot API
    const contacts = await hubspot.crm.contacts.searchApi.doSearch({
      query: input.query,
      limit: 10,
      properties: ['firstname', 'lastname', 'email', 'company']
    });
    
    // Return only essential fields (not full contact records)
    return contacts.results.map(c => ({
      id: c.id,
      name: `${c.properties.firstname} ${c.properties.lastname}`,
      email: c.properties.email,
      company: c.properties.company
    }));
  }
}