HTTP Transport

How AMP credentials are carried over HTTP.

HTTP is the primary transport for AMP. Credentials are sent as request headers, pricing is discovered via a well-known endpoint or 402 response headers.

Discovery

Well-known endpoint

Servers expose pricing at GET /.well-known/amp.json:

{
  "amp_version": "1.0",
  "recipient": "<server_pubkey_base58>",
  "program_id": "2d1B2PmumwYWuR82AbXAARTL1nrn8N7Vu9bLXTXUDmVA",
  "network": "solana:mainnet-beta",
  "pricing": {
    "default": {
      "mode": "per-call",
      "rate": "1000",
      "token": "EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v",
      "minDeposit": "1000000",
      "settleInterval": 3600
    },
    "routes": {
      "/v1/inference": { "mode": "per-call", "rate": "10000" }
    }
  }
}

402 response headers

When a request arrives without AMP credentials, the server responds with 402 Payment Required and these headers:

HTTP/1.1 402 Payment Required
AMP-Version: 1.0
AMP-Pricing: {"mode":"per-call","rate":"1000","token":"EPjFWdd5...","minDeposit":"1000000","settleInterval":3600}
AMP-Recipient: <server_pubkey_base58>
AMP-Program: 2d1B2PmumwYWuR82AbXAARTL1nrn8N7Vu9bLXTXUDmVA
AMP-Network: solana:mainnet-beta

Request credentials

Include three headers with every request:

Header	Value	Example
`AMP-Channel`	Channel PDA address (base58)	`9fhH5Jbg7VWx...`
`AMP-Seq`	Monotonic sequence number	`42`
`AMP-Sig`	Ed25519 signature of seq (base58)	`3xKn9P2b...`

The signature is computed over the sequence number encoded as a little-endian u64 (8 bytes), signed with the funder's (or delegate's) Ed25519 keypair.

Response headers

The server includes the remaining balance in the response:

AMP-Balance: 8500000

Error responses

{
  "error": "AMP_UNDERFUNDED",
  "message": "Channel balance is 500 but minimum required is 1000.",
  "channel": "<channel_pda>",
  "balance": 500
}