Circle MPP · USDC · agent identity

Machine payments need more than a payer address.

Circle’s MPP/USDC method gives agents a standard way to pay in USDC. Gregers shows the adjacent requirement: the recipient should also be able to inspect which agent acted, which wallet paid, and who is accountable behind it.

Circle announcement USDC method spec Gregers x402 receipt Verify Token #40

Thesis

MPP standardizes how agents pay. Agent ID explains who paid.

A USDC receipt proves settlement. An agent registry and hash-verified card make that settlement attributable to an accountable software actor rather than a naked wallet address.

Current Gregers proof

0.01 USDC

Gregers already paid a 0x x402 API request from a DFNS Base wallet and published the settlement receipt.

What Circle’s spec adds

Payment method

method="usdc" for intent="charge" in HTTP Payment Authentication.

Direct chains

Native USDC direct charges on EVM and Solana, plus a USDCx-on-Stacks profile.

Gateway profile

Circle Gateway can let a merchant receive USDC on a destination chain while accepting payer funds from supported source chains.

Settlement discipline

The spec is careful about receipts: success should be returned only after the selected profile has completed settlement, not merely after an estimate, submission, attestation, or pending state.

What Gregers adds

Agent registered
Gregers is Concordium Token #40.

Card hash checked
The public agent card matches the on-chain metadata hash.

Wallet attributed
The DFNS Base wallet is the payer in the USDC settlement.

Action executed
Gregers paid for an API request through x402.

Receipt published
Others can inspect both payment and identity evidence.

Evidence already live

Item	Observed value
Agent record	Gregers Token #40 · active · hash matched · wallet set · no blockers
Payer wallet	`0x4e7b9e978e87b1c62ebac82bc4507580e2f47fef`
Payment asset	Base native USDC · `0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913`
Payment amount	`10000` base units = `0.01 USDC`
Settlement tx	`0xbf52a428e4b42bacdba0966a813c8003899697b3afdfa2dc0e6a88d1b586a18e`

Receipt page

Open the x402 receipt for the decoded settlement header, Base transaction, USDC transfer, and 0x price-response evidence.

How this maps to MPP

HTTP/1.1 402 Payment Required WWW-Authenticate: Payment realm="merchant.example", method="usdc", intent="charge", id="challenge_001", request="BASE64URL_JCS_REQUEST", expires="..." Client signs USDC authorization with DFNS. Server verifies USDC settlement. Application verifies Gregers Token #40. Server returns Payment-Receipt + agent identity evidence.

Boundary

This page does not claim Circle has integrated Concordium.
The completed Gregers proof is an x402/0x paid price request, not a Circle Gateway transfer.
The near-term build target is a direct EVM method="usdc" prototype using DFNS-signed Base USDC; Circle Gateway requires separate Gateway access.