How to Wrap Claude in an API Endpoint

"Wrapping Claude in an API endpoint" means putting your own HTTP layer in front of Claude's API so other apps, services, or team members can call a single URL instead of dealing with Anthropic's SDK, your API key, and model-specific request formats directly. Instead of every client needing your ANTHROPIC_API_KEY, they hit something like POST /api/chat on your own domain, and your server handles the actual call to Claude behind the scenes.

There are two ways to do this: build the wrapper yourself, or use a service that already did it. Both are covered below, along with what actually needs to be handled once you go past a weekend prototype.

Why wrap Claude instead of calling it directly

Calling Claude directly from a frontend, mobile app, or internal tool means shipping your Anthropic API key to every client that needs access. That's a non-starter for anything public-facing, and it's fragile even internally — one leaked key and you're rotating credentials across every service that used it.

A wrapper endpoint solves this by centralizing the real API key on a server you control, and issuing your own keys or tokens to whatever calls that server. It also gives you a single place to add logging, rate limiting, retries, and usage tracking without touching every client.

Building a minimal wrapper yourself

The simplest version is a thin proxy: accept a request, forward it to Claude with your server-side key, return the response.

// server.js
import express from "express";
import Anthropic from "@anthropic-ai/sdk";

const app = express();
app.use(express.json());

const anthropic = new Anthropic({ apiKey: process.env.ANTHROPIC_API_KEY });

app.post("/api/chat", async (req, res) => {
  const { messages } = req.body;

  try {
    const response = await anthropic.messages.create({
      model: "claude-3-5-sonnet-20241022",
      max_tokens: 1024,
      messages,
    });
    res.json(response);
  } catch (err) {
    res.status(500).json({ error: err.message });
  }
});

app.listen(3000);

This works, and it's a reasonable starting point for a personal project. But it's missing almost everything you need once real traffic hits it:

• Auth for your own endpoint. Right now anyone who finds this URL can burn your Claude quota. You need to check an API key or token on every incoming request before forwarding anything.
• Rate limiting. Without it, a single misbehaving client (or a bug in your own frontend that retries in a loop) can blow through your usage in minutes.
• Streaming. Claude supports streaming responses, and a naive wrapper that waits for the full completion before responding will feel slow and burn timeout budgets on serverless platforms.
• Retries and error handling. Claude's API returns rate limit and overload errors that need backoff logic, not just a 500 passed straight to the client.
• Usage tracking per caller. If more than one person or service uses this endpoint, you'll want to know who's consuming what, especially if you're billing internally or splitting cost across teams.
• Key management. Rotating the underlying Anthropic key without breaking every client means adding a layer of indirection — your own keys, mapped to the real one.

None of this is hard individually, but together it's real infrastructure work that has nothing to do with your actual product.

Using a managed wrapper instead

If the goal is an HTTPS endpoint backed by your Claude access — not a side project in API gateway engineering — a service like SubToAPI does this out of the box. You get application API keys (sub_live_...) instead of exposing your raw Anthropic key, plus streaming, tool use, usage metadata, and team seats already wired up.

The request shape mirrors what you'd already be building:

curl https://api.subtoapi.app/v1/messages \
  -H "Authorization: Bearer $SUBTOAPI_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "claude-3-5-sonnet-20241022",
    "max_tokens": 1024,
    "messages": [
      { "role": "user", "content": "Summarize this changelog in 3 bullets." }
    ]
  }'

Same idea in JavaScript:

const res = await fetch("https://api.subtoapi.app/v1/messages", {
  method: "POST",
  headers: {
    Authorization: `Bearer ${process.env.SUBTOAPI_KEY}`,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    model: "claude-3-5-sonnet-20241022",
    max_tokens: 1024,
    messages: [{ role: "user", content: "Draft a release note for v2.3." }],
  }),
});

const data = await res.json();

Each app or service gets its own sub_live_ key, so you can revoke one without touching the others, and see usage broken down per key in the dashboard instead of guessing which client burned through the quota. Streaming and tool use work the same way they do against Anthropic directly — see the streaming docs and tool use docs for the request format.

For teams, this matters more than it looks: instead of one shared Anthropic key passed around in Slack, each teammate or environment (staging, production, a specific integration) gets its own scoped key under one account. Plans start at Solo (€9), Team (€19/seat), and Scale (€49/seat), with a free trial at signup — details on pricing.

Which approach makes sense

Build your own wrapper if the use case is a single internal tool with one trusted caller, you're comfortable owning retries and rate limiting, and you don't need multiple keys or per-caller usage data. It's a few hours of work and full control.

Reach for a managed option if more than one client or team member needs access, you want per-key usage visibility without building a dashboard, or you'd rather not maintain retry and streaming logic as Anthropic's API evolves. The quickstart covers getting a key and making your first request in a few minutes, and the messages docs cover the full request/response shape.

questions

Do I need to change my code if I already call Claude directly? Minimally. If you're using the standard messages format, switching to a wrapper usually means changing the base URL and the auth header, not rewriting request bodies.

Can a wrapped endpoint still stream responses? Yes, as long as the wrapper is built to proxy chunks rather than buffer the full response. See /docs/streaming for the expected format.

Is wrapping Claude the same as building a chatbot? No. Wrapping is the infrastructure layer — an HTTP endpoint that forwards to Claude safely. What you build on top of it (a chatbot, a summarizer, an agent) is a separate concern.