Core Abstractions

Directory reduces every routing decision to two fields: value type (what is transferred) and transfer type (how it moves). A pair of these is a complete delivery instruction.

Value Type — What You Transfer

A value type identifies the specific asset being transferred. It is the concrete asset, not a category.

Value Type	Asset
`USDC`	Circle’s USD stablecoin
`USDT`	Tether’s USD stablecoin
`USD`	US dollars (fiat)
`ETH`	Ether
`BTC`	Bitcoin
`MXN`	Mexican pesos (fiat)
`EUR`	Euros (fiat)

The value type makes no assumption about how the asset moves. USDC is USDC whether it moves on Ethereum, Base, Solana, or any future network.

Transfer Type — How You Transfer It

A transfer type identifies the network on which value moves. It is the rail, not the cargo.

Transfer Type	Network
`ethereum`	Ethereum mainnet
`base`	Base L2
`solana`	Solana
`bitcoin`	Bitcoin network
`ach`	US ACH network
`wire`	US wire transfer
`spei`	Mexico’s SPEI
`sepa`	EU SEPA
`fps`	UK Faster Payments

The transfer type makes no assumption about what asset moves on it. Ethereum carries USDC, USDT, ETH, and thousands of other tokens.

Composition

A complete delivery instruction is a value type and transfer type pair. Nothing else is needed at the protocol layer.

[
  { "value_type": "USDC", "transfer_type": "ethereum" },
  { "value_type": "USD",  "transfer_type": "ach"      },
  { "value_type": "MXN",  "transfer_type": "spei"     },
  { "value_type": "EUR",  "transfer_type": "sepa"     }
]

An operator MAY publish accepted pairs in the optional capability manifest; they MAY also declare them out-of-band. A sender matches against what it can send. If there is a match, there is a route. If not, there isn’t. The protocol does not perform conversion.

Address normalization

An address is localpart@domain or a bare domain:

The domain is converted to ASCII punycode (IDN) and lowercased.
The local part is Unicode-normalized to NFC, whitespace-trimmed, and (for lookup) lowercased.
The local part MUST be at most 64 bytes after NFC.
The full domain MUST be at most 253 bytes.
A bare domain is equivalent to the reserved local part _root on that domain.

The signed contract returns the normalized form in its address field.

Extensibility

New value types and transfer types are added without protocol changes. An operator registers a new pair and it becomes routable. No governance decisions, no protocol upgrades. The pair exists or it doesn’t.

Implementations MUST preserve unknown JSON fields verbatim in both requests and responses. A future protocol revision can add fields that existing verifiers will still canonicalize and check against the signature.