Verified against @dexterai/x402 5.3.1 · 2026-07-07
Glossary
By the end of this page you will have a plain definition for every Dexter-specific term used across these docs. Terms are alphabetical.
Crystallization
As an agent makes paid calls against a tab, each call adds to a running total the buyer owes but has not yet moved on-chain. Crystallization is the step that locks part or all of that accrued total and settles it on-chain to the seller, turning soft off-chain accrual into a final on-chain payment. In opendexter tab list you see both sides of this: spentUsdc is what has accrued against the tab, and crystallizedUsdc is how much of it has crystallized (settled on-chain) so far.
Dextercard
Your Dextercard is your Dexter account session — the sign-in that unlocks your non-custodial vault from the CLI or an MCP client. You log in with an email one-time code (opendexter dextercard login), and the session is stored locally and encrypted. Because a tab is opened against your vault, the Dextercard sign-in is the step that must come before opening a tab.
Exact scheme
One of the two payment schemes an x402 endpoint can offer. exact means you pay the precise amount for that single call, on the spot. It is the pay-per-call path — no tab required. Compare with the tab scheme, where the call is charged against an already-open spend channel. An endpoint's check output lists which schemes it supports.
Facilitator
The service that verifies an x402 payment and submits its settlement on-chain, so buyers and sellers do not have to run that plumbing themselves. When your client pays, the facilitator confirms the payment is valid and moves the funds to the seller.
Grant
The signed authorization behind a tab: it says a specific session key may spend up to a set cap with a specific seller, until an expiry. Approving a grant is what you do at the passkey approval link when you run tab connect; the cap you choose there is the tab's ceiling.
Receipt
The record that a payment settled. For an exact per-call payment, that is the settlement transaction returned alongside the response. For a tab, it is the on-chain crystallization that settles accrued spend to the seller. There is no opendexter receipts command today: to see what you have spent, use opendexter tab list (per-tab spentUsdc / crystallizedUsdc) and opendexter settings (spend.last24hUsdc).
Session key
An ephemeral key your agent uses to sign spend against an open tab, authorized only up to the tab's cap and expiry. It shows up as agentKey in opendexter tab list. Because its authority is bounded by the cap, a compromised session key can never spend more than the ceiling you approved.
Settlement
Moving the money on-chain to the seller for calls already delivered. For an exact payment, settlement happens at the call. For a tab, settlement is the crystallization transaction that pays the seller what has accrued.
Tab
A pre-approved spend channel between one buyer and one seller, capped at an amount the buyer approves. Once a tab is open, the buyer's paid calls to that seller ride the tab and settle in the background instead of each call needing a fresh on-chain payment. The buyer approves the cap once, the funds stay in the buyer's own vault, and the buyer can close the tab at any time. See Tabs — the concept.
Vault
A non-custodial on-chain account that holds your funds and enforces the spend rules you set. You keep control of it — you approve caps, and you can close a tab drawing from it. Tabs and paid calls draw from your vault within the limits you approve. You sign in to your vault with your Dextercard.
x402
The HTTP payment protocol these docs are about. When a resource needs payment, the server answers a request with HTTP 402 Payment Required and a description of the price and how to pay. The client pays and retries, and the resource is returned. Dexter's tools implement x402 version 2.