Call third-party APIs from your Worker with typed bindings

capa turns an OpenAPI spec into a Cloudflare service binding. Call it from your Worker, or let your agent call it through one MCP server. Every call returns the response and an evidence record.

Read the tutorial Browse the catalog GitHub

Call Stripe from any Worker

const { result, evidence } =
  await env.STRIPE.paymentIntents.create({
    amount: 2500,
    currency: "usd",
  });

console.log(result.id, evidence.act.status, evidence.verdict);
pi_... 200 pass

How it works

1
The provider publishes a spec
POST /v1/payment_intents
2
capa generates a typed method
paymentIntents.create(body)
3
You deploy it to your account
cf deploy
4
Your Worker or your agent calls it
env.STRIPE.paymentIntents.create(…)

When the provider changes the spec, a weekly job regenerates the binding and opens a pull request.

Every call returns evidence

The evidence record says what capa sent, what came back, and which checks passed. Log it, show it, or ignore it.

{
  operationId: "PostPaymentIntents",
  act: {
    request: { method: "POST", url: "https://api.stripe.com/v1/payment_intents" },
    status: 200,
  },
  assert: [{ kind: "httpStatus", expected: "2xx", actual: 200, passed: true }],
  verdict: "pass",
}

Call it from a Worker or an agent

From your Worker

Bind the capability and call typed methods. The API key stays in the capability Worker.

src/index.ts

const { result, evidence } =
await env.STRIPE.paymentIntents.create({
amount: 2500,
currency: “usd”,
});

Tutorial

From your agent

Connect Claude or Cursor to capa-gateway. The agent writes code that runs in a sandbox with no network access. The sandbox calls the capability through the gateway, which adds your key from your vault.

MCP tool: execute

const me = await capa.github.user.list();
return me.result.login;

Use capa from an agent

Quick start

Deploy a capability from the catalog, set its key, then bind it from your Worker.

cd capabilities/stripe
cf migrate && cf deploy
cf workers secrets update STRIPE_API_KEY --worker capa-stripe --type secret_text

env: {
  STRIPE: bindings.worker({ worker: "capa-stripe", exportName: "StripeCapability" }),
}

Using Wrangler? The tutorial shows both.

Catalog

Capabilities: 16
Operations: 6,325
Namespaces: 570

To add an API, run the codegen against its spec. Keep the result in your account, or open a pull request to add it here.

Next steps

Tutorial
Deploy a capability and call it from a Worker.
Use from an agent
One MCP server for every capability.
How it works
Service bindings, evidence, and generated code.
Runtime auth
Use one deployed Worker for many tenants.
Reference
Secrets, entrypoints, and codegen flags.

Call third-party APIs from your Worker with typed bindings

How it works

The provider publishes a spec

capa generates a typed method

You deploy it to your account

Your Worker or your agent calls it