MCP vs REST APIs: When to Use What

A common question: "Should I build a REST API or an MCP tool?" The answer: it depends. Here's how to decide.

REST APIs Are For...

• Human developers reading docs and writing integration code
• Broad consumption — web apps, mobile apps, third-party integrations
• CRUD operations — standard create, read, update, delete patterns
• Existing infrastructure — you already have REST, keep it

MCP Tools Are For...

• AI agents that need to discover and invoke capabilities dynamically
• Semantic understanding — agents need descriptions, not just endpoints
• Composability — agents chain multiple tools together in a single workflow
• Rapid iteration — add tools without updating agent code

The Hybrid Approach

The best strategy? Wrap your REST API with MCP.

// Your existing REST endpoint
app.get('/api/weather/:city', weatherHandler);

// MCP wrapper (adds discovery + semantics)
server.addTool({
  name: "get_weather",
  description: "Get current weather for any city worldwide",
  parameters: { city: { type: "string" } },
  handler: async ({ city }) => {
    const resp = await fetch(`/api/weather/${city}`);
    return resp.json();
  }
});

Decision Matrix

Factor	REST	MCP
Human consumers	✅ Best	❌
AI agent consumers	⚠️ Possible	✅ Best
Auto-discovery	❌	✅ Native
Semantic contracts	Manual docs	✅ Built-in
Existing ecosystem	✅ Huge	🚀 Growing

The Takeaway

Don't choose — build both. REST for your human-facing API. MCP as the AI-native layer on top. mcpm makes publishing both straightforward.

How are you bridging REST and MCP? Let's discuss.

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