Build your first judgement

Set TAKUSEN_API_URL to the API origin and choose the EVM wallet that will pay for requests. Takusen uses prepaid USDC credits: the wallet deposits USDC into one settlement domain's escrow, and the API exposes the observed amount as credits on that domain. Credits never move between domains automatically.

curl "$TAKUSEN_API_URL/v1/chain"

Choose a domain whose active and healthy fields are true. Save its domainId, chainId, USDC contract, escrow address, and one advertised depositMechanisms value. Your wallet needs that domain's USDC plus enough native gas for any wallet-submitted transactions.

For an API integration, request a deposit plan. amountMicros uses micro-USDC, so 10000000 means 10 USDC. Use a mechanism advertised by /v1/chain.

curl --request POST "$TAKUSEN_API_URL/v1/credits/deposit" \
  --header 'Content-Type: application/json' \
  --cookie takusen.cookies \
  --data '{
    "settlementDomain": "0x<domainId>",
    "amountMicros": 10000000,
    "mechanism": "eip3009"
  }'

The deposit is spendable only after Native Chain observation. Poll /v1/credits with the session cookie until the selected account's availableMicros is at least the request's spendLimitMicros. depositedMicros includes observed funding; reservedMicros is committed to active requests; spentMicros is finalized execution cost.

curl --cookie takusen.cookies "$TAKUSEN_API_URL/v1/credits"

curl "$TAKUSEN_API_URL/v1/models"
curl "$TAKUSEN_API_URL/v1/output-schemas"

Choose active model IDs from /v1/models and a governed output type from /v1/output-schemas. Do not hard-code these values across protocol revisions.

{
  "settlementDomain": "0x<domainId returned by /v1/chain>",
  "prompt": "Will the stated resolution condition be satisfied?",
  "outputType": "boolean",
  "models": ["openai/gpt-6-luna", "anthropic/claude-haiku-5.5"],
  "spendLimitMicros": 250000,
  "timeLimitSeconds": 90,
  "executionQuorum": 2,
  "visibility": "public"
}

spendLimitMicros is the maximum all-in reservation in micro-USDC: 250000 is 0.25 USDC. Keep the serialized body unchanged through the challenge and submission calls.

curl --request POST \
  --url "$TAKUSEN_API_URL/v1/x402/requests" \
  --header 'Content-Type: application/json' \
  --dump-header response.headers \
  --data @request.json

402 Payment Required is the expected response. Decode the PAYMENT-REQUIRED header or read the equivalent JSON body. It contains the exact network, asset, escrow, amount, one-use challenge ID, AuthorizeRequest typed data, and extensions.takusen.binding for an on-chain consumer. The challenge expires after ten minutes, leaving time to confirm the application binding before payment.

1. Sign the exact extensions.takusen.authorization EIP-712 typed data with the funded payer wallet.
2. Create an x402 v2 PaymentPayload using the selected accepts entry. Set extensions.takusen.challengeId, requester, and requestSignature.
3. Base64-encode that JSON payload as PAYMENT_SIGNATURE.
4. POST the unchanged request.json again with PAYMENT-SIGNATURE. A successful response is 202 Accepted and contains the requestId.

curl --request POST \
  --url "$TAKUSEN_API_URL/v1/x402/requests" \
  --header 'Content-Type: application/json' \
  --header "PAYMENT-SIGNATURE: $PAYMENT_SIGNATURE" \
  --data @request.json

curl --no-buffer "$TAKUSEN_API_URL/v1/requests/$REQUEST_ID/stream"
curl "$TAKUSEN_API_URL/v1/requests/$REQUEST_ID"
curl "$TAKUSEN_API_URL/v1/requests/$REQUEST_ID/answers"

Public requests need no session for streaming or reads. Reconnect the SSE stream with Last-Event-ID until the request reaches a terminal state, then inspect the aggregate record, model answers, evidence hashes, measured spend, and settlement transaction.