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.

<span class="hljs-comment">// Your existing REST endpoint</span>
app.<span class="hljs-title function_">get</span>(<span class="hljs-string">&#x27;/api/weather/:city&#x27;</span>, weatherHandler);

<span class="hljs-comment">// MCP wrapper (adds discovery + semantics)</span>
server.<span class="hljs-title function_">addTool</span>({
  <span class="hljs-attr">name</span>: <span class="hljs-string">&quot;get_weather&quot;</span>,
  <span class="hljs-attr">description</span>: <span class="hljs-string">&quot;Get current weather for any city worldwide&quot;</span>,
  <span class="hljs-attr">parameters</span>: { <span class="hljs-attr">city</span>: { <span class="hljs-attr">type</span>: <span class="hljs-string">&quot;string&quot;</span> } },
  <span class="hljs-attr">handler</span>: <span class="hljs-title function_">async</span> ({ city }) =&gt; {
    <span class="hljs-keyword">const</span> resp = <span class="hljs-keyword">await</span> <span class="hljs-title function_">fetch</span>(<span class="hljs-string">`/api/weather/<span class="hljs-subst">${city}</span>`</span>);
    <span class="hljs-keyword">return</span> resp.<span class="hljs-title function_">json</span>();
  }
});

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.

#MCP #REST #APIDesign #AIAgents #mcpm