Keep real keys private with OpenAI Responses.

// npm install openai deny-sh@^2.2.0
import OpenAI from 'openai';
import { vaultGet } from 'deny-sh/client';

const client = new OpenAI();
const tools = [{
  type: 'function' as const,
  name: 'get_invoice',
  description: 'Look up a Stripe invoice by id',
  strict: true,
  parameters: {
    type: 'object',
    properties: { id: { type: 'string' } },
    required: ['id'],
    additionalProperties: false,
  },
}];

let resp = await client.responses.create({
  model: 'gpt-5.5',
  input: 'Look up invoice in_1Abc123XYZ',
  tools,
});

// Walk function_call items, resolve server-side, send results back.
while (true) {
  const calls = resp.output.filter(o => o.type === 'function_call');
  if (calls.length === 0) break; // model is done; resp.output_text is the answer

  const outputs = [];
  for (const call of calls) {
    if (call.name === 'get_invoice') {
      const { id } = JSON.parse(call.arguments);
      // resolve the credential INSIDE the tool boundary
      const stripeKey = await vaultGet('stripe-prod', process.env.VAULT_PW!);
      const r = await fetch(`https://api.stripe.com/v1/invoices/${id}`, {
        headers: { Authorization: `Bearer ${stripeKey}` },
      });
      // narrowed DTO: pick only the fields the model needs. Never return
      // raw upstream JSON, error bodies, or response headers to the model.
      const body = r.ok ? await r.json() : null;
      const dto = body
        ? { id: body.id, amount_due: body.amount_due, status: body.status }
        : { error: 'invoice_lookup_failed', status: r.status };
      outputs.push({
        type: 'function_call_output' as const,
        call_id: call.call_id,
        output: JSON.stringify(dto),
      });
    }
  }
  resp = await client.responses.create({
    model: 'gpt-5.5',
    previous_response_id: resp.id, // chain server-side state
    input: outputs,
    tools,
  });
}

# pip install openai deny-sh requests
import os, json, requests
from openai import OpenAI
from deny_sh import vault_get

client = OpenAI()
tools = [{
    "type": "function",
    "name": "get_invoice",
    "description": "Look up a Stripe invoice by id",
    "parameters": {
        "type": "object",
        "properties": {"id": {"type": "string"}},
        "required": ["id"],
        "additionalProperties": False,
    },
}]

resp = client.responses.create(
    model="gpt-5.5",
    input="Look up invoice in_1Abc123XYZ",
    tools=tools,
)

while True:
    calls = [o for o in resp.output if o.type == "function_call"]
    if not calls:
        break  # model is done; resp.output_text is the answer
    outputs = []
    for call in calls:
        if call.name == "get_invoice":
            args = json.loads(call.arguments)
            # resolve the credential INSIDE the tool boundary
            stripe_key = vault_get("stripe-prod", os.environ["VAULT_PW"])
            r = requests.get(f"https://api.stripe.com/v1/invoices/{args['id']}",
                headers={"Authorization": f"Bearer {stripe_key}"})
            # narrowed DTO: never feed raw upstream JSON back to the model
            if r.ok:
                b = r.json()
                dto = {"id": b.get("id"), "amount_due": b.get("amount_due"), "status": b.get("status")}
            else:
                dto = {"error": "invoice_lookup_failed", "status": r.status_code}
            outputs.append({
                "type": "function_call_output",
                "call_id": call.call_id,
                "output": json.dumps(dto),
            })
    resp = client.responses.create(
        model="gpt-5.5",
        previous_response_id=resp.id,
        input=outputs,
        tools=tools,
    )