# AffixIO agentic payment verification

Canonical page: https://www.affix-io.com/agentic-payment-verification/
This brief: https://www.affix-io.com/agentic-payment-verification/llms.txt
Site brief: https://www.affix-io.com/llms.txt
SDK: https://www.npmjs.com/package/affixio (npm install affixio)
GitHub: https://github.com/AffixIO/SDK
Hub: https://hub.affix-io.com/
API: https://api.affix-io.com
Related: https://www.affix-io.com/docs/ https://www.affix-io.com/how-it-works/ https://www.affix-io.com/for-agents/
Last updated: 2026-09-01

## What this page is

For autonomous payment agents, Affix.io provides zero-PII cryptographic proof that payment intent was created and completed. Local prove on your host, replay-safe, machine-verifiable, ML-DSA-65 (FIPS 204) signatures. Personal data never leaves your stack.

## Key methods

- AffixSDK.prove({mode, circuitId, fields}) - the "payment intent" shape uses circuit simple_yesno, with fields like {claim: "pay.intent", required: "pay.intent"}.
- AffixSDK.verifyLocal(circuitId, proof, {envelope}) and POST /v1/verify for remote attestation.
- createAgentTrust().enrol / .authorise - Know Your Agent capability bound to agent identity, PII-free.
- SpentJournal - append-only, hash-chained, ML-DSA-65 per entry (replay protection).
- buildMerkleTree / GET /v1/merkle/root - audit root for batches of legs.

## Typical wiring

1. Install affixio and store a Hub key.
2. Configure apiBase (default https://api.affix-io.com); mode offline|auto|online.
3. Prove intent before funds move (fields incl intentId, amount, payee).
4. Attach the proof envelope as provider idempotency key or metadata.
5. Recipient calls verifyLocal() or the API, and optionally Merkle-anchors the leaf.

## Do not claim

- HMAC proofs are not zero-knowledge (UltraHonk is the ZK mode).
- Do not cite scoped npm names as current (@affix-io/sdk was unpublished).
- No browser SDK (no WASM prover in this package).
- No FIPS 140-3, ISO 27001, or SOC 2 claim.