Call the service endpoint without payment headers.
Receive HTTP 402 with WWW-Authenticate: Payment header AND x402 accepts[] array in response body.
Select a paymentRequirement from accepts[] matching your preferred network + asset.
Networks: cardano:mainnet (ADA, DJED, iUSD, USDCx, USDM), stellar:pubnet (USDC, XLM), sandbox (free).
Send payment to the payTo address for maxAmountRequired in the specified asset.
Stellar fee sponsorship: POST your signed XDR to https://ai-service-hub-15.emergent.host/api/mpp/stellar/sponsor — NEXUS pays gas, you need 0 XLM.
Retry with X-PAYMENT: <base64url JSON {x402Version:1, scheme:"exact", network, payload:{tx_hash, currency}}> header.
Parse the JSON response and X-PAYMENT-RESPONSE header.

Option B: MPP Standard

Call the service endpoint without payment headers.
Receive HTTP 402 with WWW-Authenticate: Payment header listing all accepted currencies and amounts.
Pick your preferred chain + currency: Cardano (ADA, stablecoins) or Stellar (USDC, XLM).
Create payment: Masumi escrow (Cardano) or direct Stellar transfer.
Stellar fee sponsorship: POST your signed XDR to https://ai-service-hub-15.emergent.host/api/mpp/stellar/sponsor — NEXUS pays gas, you need 0 XLM.
Retry with Authorization: Payment <base64url-credential> header.
Parse the JSON response and Payment-Receipt header.

Option C: Legacy Header

Send a POST request to the NEXUS API endpoint with your input.
Include the X-Payment-Proof header (Masumi payment ID or sandbox_test for testing).
Parse the JSON response and return the result.

API Call

curl -X POST https://ai-service-hub-15.emergent.host/api/original-services/cron-builder \
  -H "Content-Type: application/json" \
  -H "X-Payment-Proof: $NEXUS_PAYMENT_PROOF" \
  -d '{
  "input": "Example input for Cron Expression Builder"
}'

Endpoint: https://ai-service-hub-15.emergent.host/api/original-services/cron-builder Method: POST Headers:

Content-Type: application/json
X-PAYMENT: <base64url JSON> (x402 standard — recommended)
Authorization: Payment <credential> (MPP standard)
X-Payment-Proof: <masumi_payment_id> (legacy — use sandbox_test for free testing)

Accepted Currencies: ADA, DJED, iUSD, USDCx, USDM (Cardano) | USDC, XLM (Stellar) x402 Discovery: GET https://ai-service-hub-15.emergent.host/api/mpp/x402 (all services in native x402 format) MPP Discovery: GET https://ai-service-hub-15.emergent.host/api/mpp/discover Stablecoin Registry: GET https://ai-service-hub-15.emergent.host/api/mpp/stablecoins (includes on-chain policy IDs) Stellar Info: GET https://ai-service-hub-15.emergent.host/api/mpp/stellar (assets, recipient, fee sponsorship) Fee Sponsorship: POST https://ai-service-hub-15.emergent.host/api/mpp/stellar/sponsor (NEXUS pays Stellar gas — agents need 0 XLM)

External Endpoints

URL	Method	Data Sent
`https://ai-service-hub-15.emergent.host/api/original-services/cron-builder`	POST	Input parameters as JSON body

Security & Privacy

All data is sent to https://ai-service-hub-15.emergent.host over HTTPS/TLS.
No data is stored permanently; requests are processed and discarded.
Payment proofs are verified on the Cardano blockchain via the Masumi Protocol.
No filesystem access or shell execution required.

Model Invocation Note

This skill calls the NEXUS AI service API which uses LLM models (GPT-5.2, Claude Sonnet 4.5, GPT-4o) to process requests. The AI processes your input server-side and returns a structured response. You may opt out by not installing this skill.

Trust Statement

By using this skill, your input data is sent to NEXUS (https://ai-service-hub-15.emergent.host) for AI processing. Payments are non-custodial via the Masumi Protocol on Cardano. Only install if you trust NEXUS as a service provider. Visit https://ai-service-hub-15.emergent.host for full documentation.

nexus-cron-builder

Cron Expression Builder

When to use

Steps

Option A: x402 Standard (Recommended)