Creating a market

Creating a claim means committing USDC to one side of a question you believe you are right about. This guide covers what makes a claim settleable, and what happens mechanically when you publish it.

Prerequisite: a connected wallet on Testnet with XLM and USDC. See Connecting a wallet.

What a claim consists of

Field	What it is
Question	One verifiable question about a future outcome
Your position	The side you are staking on
Counter position	The side a challenger takes
Resolution URL	The exact source the oracle will read to settle
Settlement rule	Plain-language criteria the evidence must satisfy
Deadline	When the market locks and becomes settleable
Category	sports, weather, crypto, culture or custom
Your stake	USDC, minimum 2 USDC
Odds mode	pool (pari-mutuel) or fixed (guaranteed multiple)
Max challengers	Up to 100. Set to 1 for a duel
Private?	Optionally gate joining behind an invite key

A good example:

Will BTC close above $100,000 USD on 2026-05-25 according to CoinGecko?

Choosing a resolution URL — the part that matters most

A claim is only as good as the URL that settles it. Four rules, each of which exists because breaking it produces a market that cannot settle cleanly:

It returns the answer, not a page about it

JSON with the number in it. A news article that describes the outcome in prose reads differently to a language model on two different days.

It still answers after the deadline

An endpoint that serves only what is upcoming goes blank at exactly the moment the oracle needs it. Point at the specific record, never at a list that the record eventually falls off.

It is stable byte for byte

sha256 of the response goes on chain. A page carrying a rotating banner, an ad slot or a render timestamp hashes differently on every fetch — which destroys the one property that makes the oracle checkable by anyone else.

The oracle can reach it unauthenticated

Settlement re-fetches the same URL from a different process, possibly days later. A key you held and the oracle does not is a claim that cannot settle.

Source families that work well

Prices — CoinGecko. Deep history, unambiguous numbers. Weather — Open-Meteo. No key required, fixed coordinates, forecast checkable against what was actually observed. Launches — Launch Library 2. Scheduled events that genuinely slip, with a per-launch record that survives the date.

Avoid one-bet-sold-many-times

A board of nothing but will BTC close above X is not eighteen markets — it is one bet sold eighteen times. A single move in a single asset resolves all of them the same way, and anyone who reads that move correctly sweeps the board without having been right about anything else. Variety is what makes a prediction market informative.

Writing the settlement rule

The settlement rule is the sentence the model is judged against. Be explicit about:

• The exact threshold, including the comparison — above, at or above, below.
• The units and currency.
• The timezone for any date or time boundary.
• Which field of the response counts, if the response has several.
• What happens on ambiguity — though note that the oracle already has DRAW and UNRESOLVABLE available and prefers refunding over guessing.

Vague rules do not produce arbitrary winners in Mimir; they produce refunds. That is safer, but it also means the market was pointless.

Setting a deadline

• The deadline is when the market locks. After it passes, the oracle can settle.
• Challenges landing within the last 60 seconds before the deadline are rejected by the contract. That anti-sniping window stops someone from waiting until the outcome is already observable and slipping in a zero-risk bet.
• Leave enough margin for the source to actually publish the answer. For sports, the first-party market-creator agent enforces a deadline at least 4 hours after kickoff — a good rule to borrow.

Pool odds vs fixed odds

Mode	How it pays
Pool (pari-mutuel)	Challengers share your stake proportionally to their own stakes. If you are right, you take the whole pot
Fixed odds	You guarantee challengers a return multiple, backed by your own liquidity. Payout is predictable before anyone joins. Default is 2× (20_000 bps)

In fixed-odds mode, unspent creator liability is refunded to you without a fee if challengers win.

For a duel, set max_challengers = 1; the contract enforces equal stakes.

Publishing: what actually happens

1. You sign one transaction. It carries an authorisation entry permitting exactly one USDC transfer of exactly your stake amount — no allowance is granted and nothing is left behind.
2. create_claim runs. The contract escrows your stake, asserting the escrow balance moved by exactly the requested atomic amount.
3. The current fee policy is snapshotted onto your claim. A later policy change cannot rewrite the economics of your market.
4. The claim is stored with state = Open and gets a claim_id.
5. Your claim appears in the explorer feed for challengers to find. If you made it private, share the invite link.

Minimum stake is 2 USDC (2_0000000 atomic at 7 decimals).

After you publish

Situation	What happens
Someone challenges	State moves to Active. Both sides are funded and the market waits for the deadline
Nobody challenges and the deadline passes	You can cancel the claim and get your full stake back. Zero fee
The market is challenged and settles in your favour	You are paid during resolution — no action needed from you
The market settles against you	Winning challengers pull their shares from escrow
Verdict is DRAW or UNRESOLVABLE	Everyone is refunded in full, zero fee

Fees, briefly

Fees are charged on profit only — gross - principal, floored at zero. You can never receive less than your principal back. Nothing is charged at deposit, so a market that never resolves costs you nothing. Refunds are always full.

Full schedule: Wallets, fees and payments.

Rematches

A rematch is not a separate feature — it is a new create_claim with parent_id set to the settled claim. That links the two on chain, which is what powers the rivalry and ladder surfaces.

Read next

• Challenging and settlement
• Claiming a payout