The problem
Companies and automated agents receive boleto data all the time — from an ERP, a billing system, an email, another agent. Before trusting or paying, they need an independent integrity check: is the data that arrived the same data the issuer registered?
Today that check is expensive to set up: it takes a commercial agreement, credentials, an API key, a monthly plan. For an agent making one lookup, that is far too much friction — and the practical result is that the check simply never happens.
A verification should cost the price of a verification. No contract, no subscription, no onboarding.
Data without provenance
The boleto reaches the ERP with no proof it was not altered along the way.
Credential friction
An API key and a monthly plan for someone who only needs one lookup.
Cost you cannot measure
With no price per call, the cost of verifying cannot be attributed to the process that asked for it.
Agents with no way to pay
An AI agent does not open an account, sign a contract, or hold a credit card.
The solution: Guardian402
Guardian402 is a pay-per-use API: each verification call costs 0.01 USDC, charged through the x402 protocol on Stellar. No API key, no subscription, no sign-up. The client calls, receives an HTTP 402 with payment instructions, settles, and gets the answer.
Verification is hash-based: the service recomputes the fingerprint of the boleto fields it received and compares it against the integrity proof registered in a Soroban contract. Nothing beyond the hash needs to be on-chain.
One verification — from any ERP or agent — is one measurable USDC payment.
Why it is different
Priced per call, not per contract
0.01 USDC per verification, settled on the spot through x402.
ERP-agnostic
Works with any source that sends the expected fields. TOTVS Protheus is the reference case, not a requirement.
On-chain proof, not a database
The integrity reference lives in a public, auditable Soroban contract.
Agent-ready
An AI agent pays for and consumes the endpoint on its own — no human onboarding.
How it works
From the ERP or agent call to the answer read from Soroban, in four steps:
Call
POST /v1/verify with boleto fields, as an ERP or agent would send them.
HTTP 402
The response carries the x402 payment instructions.
Settlement
The client authorizes and settles 0.01 USDC on Stellar Testnet.
Answer
Returns AUTHENTIC, MISMATCH, NOT_FOUND or REVOKED, read from Soroban.
ERP / AGENT GUARDIAN402 SOROBAN (Stellar)
+-------------------+ +--------------------+ +-------------------+
| POST /v1/verify |---->| 402 + x402 payment | | Integrity proof |
| (boleto fields) | | instructions | | (registered hash) |
+-------------------+ +---------+----------+ +---------+---------+
^ | |
| 0.01 USDC | settlement |
| v |
| +--------------------+ compares |
+----------------| AUTHENTIC / |<--------------+
result | MISMATCH / |
| NOT_FOUND /REVOKED |
+--------------------+
Possible outcomes
AUTHENTICData matches the active integrity proof registered on-chain.MISMATCHThe identifier exists, but the supplied boleto data diverges.NOT_FOUNDNo proof is registered for that boleto identifier.REVOKEDThe proof existed and was revoked by the issuer admin.Guardian402 verifies whether supplied data matches a previously registered integrity proof. It does not confirm bank settlement or payment status.
Why Protheus shows up in the examples
TOTVS is Brazil's largest business-software company, and Protheus is the ERP where a large share of Brazilian companies issue and manage boletos (bank payment slips). In the latest FGV-Eaesp IT survey, TOTVS holds about 34% of Brazil's overall ERP market (tied with SAP) and about 50% among smaller deployments (up to ~180 users).
That makes Protheus the natural reference case for demos in Brazil. Guardian402 itself, however, does not require Protheus: the same hash-based check works for boleto data from any ERP, billing system or agent that sends the expected fields.
Source: FGV-Eaesp Annual IT Use Survey (Brazil ERP market share).
Environment facts
Price per call
$0.01 USDC
Network
Stellar Testnet
Payment protocol
x402
One verification. One payment. No contract.
Let your ERP or your agent check a boleto's integrity paying only for what it looked up.