# Machine Payments Protocol (MPP)

Challenge, Credential and Receipt over HTTP 402, on the rail your rules choose.

Cohorts: Mm + Fi + Sc

**Designed.** Protocol support is designed. The flow follows the protocol's published specification, with insimbi on the merchant side. Every check and every settlement is written to the record.

**Machine Payments Protocol (MPP).** Designed. MPP's Challenge, Credential and Receipt over HTTP 402.

Lanes: Client (agent), Merchant API, insimbi, Payment method (rail or regulated partner)

1. Client (agent) to Merchant API: Request a resource
2. Merchant API to insimbi: Price it and pick the payment methods your rules allow
3. Merchant API to Client (agent): 402 Payment Required with WWW-Authenticate: Payment (the Challenge)
4. Client (agent) to Payment method (rail or regulated partner): Pay with the method the Challenge names
5. Client (agent) to Merchant API: Retry with Authorization: Payment (the Credential)
6. Merchant API to insimbi: Verify the Credential is bound to the original Challenge
7. insimbi to Payment method (rail or regulated partner): Confirm the payment
8. Payment method (rail or regulated partner) to insimbi: Confirmed
9. insimbi: Write the ledger entry and fee lines to the record
10. Merchant API to Client (agent): 200 with a Payment-Receipt header

- [All flows](/docs/flows/): Every sequence diagram, linked to its section.
- [Integrations](/integrations/#protocols): Every agent protocol and rail we connect.
- [MCP tools](/docs/mcp/): insimbi as tools for any MCP client.

Request access: sales@insimbi.net

_insimbi is in early access with design partners._