x500 | Devpost

Presenting x500!
Dashboard
Example Agent Chat
x500-sdk npm package

Inspiration

When a paid service fails, a human can call customer support. Agents cannot.

As AI agents pay for more APIs on their own - weather, search, tools, data etc.. a failed or slow response after payment leaves them with no recourse. x402 makes agent-to-API payments real; x500 asks the next question: who refunds a 500 after the agent already paid?

What it does

x500 is a micro-insurance for AI agent's x402 based API payments.

Agents call merchant APIs through an insured gateway
Merchants get paid via x402 Exact
Agents pay a flat insurance premium from on-chain escrow
If the call fails or misses SLA, the protocol refunds them automatically - no tickets, no claims desk

Try it live: dashboard · chat demo (normal + SLA-breach refund) · pitch · demo video

Who benefits

Merchants

List a paid API once and receive HBAR per call via x402
Set slug, origin URL, API price, and SLA in the dashboard
Stay focused on serving the API — premiums and refunds settle in the protocol
Become discoverable to agents that resolve your origin through x500

Agent builders

One insured fetch path: pay the merchant + pay the premium
Automatic parametric refunds on failure / SLA breach
No need to know the merchant slug — pass the public origin URL
Drop-in SDK for any agent runtime (CLI, LangChain, custom bots)

How merchants use x500

Host an HTTP API with a public HTTPS origin (e.g. ngrok for demos)
Open the dashboard → Merchants
Connect HashPack and register slug, origin, API price, and SLA
Serve the route with x402 Exact HBAR — agents reach you through the insured proxy

How agents use x500

Install the SDK, fund escrow once, then call any registered merchant by origin URL:

npm install x500-sdk
import { createX500 } from "x500-sdk";
const x500 = createX500({
  network: "testnet",
  accountId: process.env.X500_AGENT_ACCOUNT_ID!,      // 0.0.x
  privateKey: process.env.HEDERA_AGENT_PRIVATE_KEY!, // ECDSA hex 0x...
});
// 1. Fund insurance escrow once
await x500.setup({ escrowTinybars: 50_000_000n }); // 0.5 HBAR
// 2. Call a registered merchant by origin URL — slug resolved automatically
const res = await x500.fetchMerchant(
  "https://your-merchant.example/paid/weather?city=Paris",
);
console.log(res.status, await res.text());
await x500.close();

How we built it

End-to-end stack:

Contracts — X500Registry, X500Pool, X500Settler
Agent SDK / CLI — x500-sdk, x500 (npm)
Market proxy + wrap/classifier — route, classify outcomes, price premium/refund
Facilitator — x402 Exact HBAR verify & settle
Settler + indexer — on-chain settleBatch + mirror sync API
Dashboard — HashPack merchant registration & explorer
Examples — merchant server + LangChain agent

Challenges we ran into

Keeping x402 merchant payment and insurance escrow as separate rails without confusing agents or merchants
Making outcomes parametric (HTTP status / latency → refund) instead of subjective claims
Reliable settlement: idempotent callIds, settler batching, and readable Hashscan links in demos
Machine-specific client quirks (e.g. Node 22 + node-fetch vs native fetch for Groq in the example agent)

Accomplishments that we're proud of

A full path from register → pay → insure → refund on Hedera testnet
Published x500-sdk and a HashPack-powered dashboard
Live chat demo for success and SLA-breach refund scenarios
Clear separation: merchants keep their x402 servers; x500 only settles risk

What we learned

Agent commerce needs refunds as much as payments
Parametric triggers beat manual claims for autonomous callers
Hedera primitives (x402 Exact, HSCS contracts, mirror reads) are a strong fit for prepaid escrow + settlement
Good demos need honest payment breakdowns and explorer links, not just “it worked”