AirnodeHub Hackathon

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Any API in your contract ​

Challenge overview and quick start · TUM Blockchain & AI Hackathon · 30–31 October 2026 · Munich

Real-world data. Checked by your contract. Bring real-world data on-chain and let your contract check it itself. About 50 APIs, one signature check, no oracle network.

The challenge ​

Build an app or agent whose core on-chain functionality depends on signed data from AirnodeHub. Your contract authenticates the response from the expected Airnode, checks that it answers the intended request and is timely, then acts on it. A standalone API call or a decorative data display is not enough.

A contract can't call an API, so someone has to bring the data to it: a user, a keeper bot or an agent. That messenger could edit a flight status, a price or a match result. An Airnode signature lets the contract check who signed the response and whether it was altered, without trusting the messenger. It does not prove the underlying facts are correct: your app still relies on the chosen data source and Airnode operator.

AirnodeHub lists about 50 APIs: flights, weather, earthquakes, sports and esports results, market prices, DeFi, company registries and more. Each one is served through an Airnode, which signs every response with an Ethereum key. Your contract verifies the signature itself. There is no oracle network to integrate and no callback to wait for: whoever holds a signed response submits it in their own transaction.

Prizes ​

€2,000 prize pool, paid in USDC by the hackathon organisers. The indicative first, second and third place split is €1,000 / €600 / €400.

The proposed prize split is tentative. API3 reserves the right to award the entire prize pool to a single outstanding submission where its quality and novelty warrant it, or to distribute prizes more evenly among submissions that are closely matched in quality. Final allocations will be determined by API3’s judges. Prizes will be paid in USDC by the hackathon organisers.

How it works ​

  1. Pick an API on AirnodeHub. An Airnode serves each listing and signs every response with an Ethereum key. Integrations shows which listings have enough quota for the hackathon.
  2. Fetch a signed response for the request that your contract expects.
  3. Submit it to your contract. Anyone can do this: a user, a keeper bot or an agent.
  4. The contract verifies, then acts. It checks the signer, the request and the time, then reads the fields that it needs and acts on them.

Start from the starter template. It runs this flow for a Nodary ETH/USD price, and you adapt it to any listing. From API to contract walks through each step.

Any chain whose contracts can verify a secp256k1 signature over a keccak256 hash works, so you are not tied to one chain.

Paying for data with x402 ​

Most operations are priced with x402 during the hackathon. You pay in test dollars on Base Sepolia, so calls cost nothing real: testnet USDC from Circle's faucet, or AirnodeHub USD (aUSD), API3's test dollar, from its own faucet. An Airnode charges the same amount in either, and the account needs no ETH for the facilitated payment transfer. Minting aUSD and sending application transactions still require the appropriate gas token. The starter template already pays for a priced call. Paying with x402 has the token addresses, the aUSD faucet and the client code.

The autonomous agent bonus rewards a core workflow that runs over time: the agent decides when and which data to fetch, pays through x402 when required, and acts on-chain without a person initiating every cycle. Using x402 alone, making a single call, or finding an API once through MCP does not earn the bonus.

Ideas ​

Build around a decision or state change that requires authenticated data. Funds do not have to move. These are starting points, not separate tracks; check that the selected API provides the fields, history and update frequency your use case needs.

Starting pointExplore
An agent whose trading or lending actions depend on authenticated market data and explicit limitsNodary, Hyperliquid, Morpho
A payment or escrow released when authenticated external data meets a conditionUSGS Earthquakes, PandaScore, Companies House
A protocol safeguard that pauses or adjusts an on-chain position when a signed value crosses a thresholdNodary, DefiLlama

These are prompts, not prescribed projects. Original ideas are welcome. Check the current integrations and shared quotas before choosing an operation.

Requirements ​

Signed data must be essential to the application. To qualify, your submission needs:

  • A deployed contract that verifies an Airnode signature and uses the signed data in its core workflow. A testnet deployment is sufficient.
  • Signer, request and time checks that suit the use case. Where it matters, also check the time of the observation and prevent the same response from triggering the action twice, as Verify, then act explains.
  • A working demo and a public repository with setup instructions, the deployment network and the contract address.
  • A way for the judges to submit their own responses through your app or a documented script, so that they can run the tamper test below.
  • A short explanation of who relies on the data, what goes wrong if it is forged, and what data you wanted but could not find on AirnodeHub.

Judging ​

Eligible projects are scored out of 100, with up to 10 additional points for the autonomous agent flow (110 maximum). The projects that win solve a real problem where authenticating the data makes a meaningful difference.

CriterionWeightWhat we look for
Real use case40%It solves a real problem for someone who would use it, or pay for it.
Signed data matters30%The project works only because the contract checks the data. With an unsigned API call, anyone could fake the outcome.
Execution20%It works end to end in the demo.
Novelty10%An original application, mechanism or use of authenticated data, beyond the unchanged starter.
Agent bonus+10 pointsYour agent runs the core workflow over time: chooses data, pays through x402 when required, and acts on-chain without a person starting every cycle.

For the agent bonus, demonstrate repeated autonomous cycles and explain the schedule, spending limits and failure handling. x402 payment alone is not sufficient. Respect shared quotas with bounded polling, caching and backoff.

The tamper test is a pass/fail eligibility check. First show a valid, timely response for the configured signer and request producing the intended on-chain action. Then show that each of these invalid responses is rejected before that action:

  1. A real response with one value edited.
  2. A real response that is too old for your use case.
  3. A real response to a different request, such as another flight.
  4. A response we signed ourselves, with a key that is not the Airnode's.

Good to know ​

  • The upstream APIs have quotas that every team shares, so cache responses and do not poll in a loop. Integrations lists the limits of each listing.
  • On Nodary, the data source runs the Airnode itself. On the other listings, API3 runs the Airnode over the provider's API and attests to what that API returned.
  • For help, find the API3 mentors at the event, or ask in the API3 Support topic of the official TUM Blockchain & AI Hackathon Telegram group.

Resources ​