



Internet Engineering Task Force                                 E. Spink
Internet-Draft                                           Agentir Network
Intended status: Informational                               15 May 2026
Expires: 16 November 2026


              Agent Execution and Payment Protocol (AEPP)
                         draft-agentir-aepp-00

Abstract

   This document defines the Agent Execution and Payment Protocol
   (AEPP), a standardized protocol layer for executing AI agents and
   verifying payment for agent tasks on the open internet.  AEPP
   provides the missing execution and payment layer for existing agent
   URI schemes and naming services including agent://, ai://, mcp://,
   ANS, and DNS-AID.  It defines a three-phase execution model:
   discovery, payment, and execution, with on-chain payment verification
   and cryptographic receipts.  A reference implementation serving
   1,800,000 agents with zero per-agent fees is live at a2a.agentir.com.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 16 November 2026.

Copyright Notice

   Copyright (c) 2026 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components



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   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Protocol Overview . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Phase 1 — Discovery . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  Request . . . . . . . . . . . . . . . . . . . . . . . . .   4
     4.2.  Response  . . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  Phase 2 — Payment . . . . . . . . . . . . . . . . . . . . . .   5
     5.1.  Reference Payment Implementation  . . . . . . . . . . . .   5
     5.2.  Autonomous Payment Example  . . . . . . . . . . . . . . .   6
   6.  Phase 3 — Execution . . . . . . . . . . . . . . . . . . . . .   6
     6.1.  Request . . . . . . . . . . . . . . . . . . . . . . . . .   6
     6.2.  Payment Verification  . . . . . . . . . . . . . . . . . .   7
     6.3.  Response  . . . . . . . . . . . . . . . . . . . . . . . .   7
   7.  Universal Clip  . . . . . . . . . . . . . . . . . . . . . . .   7
     7.1.  Supported Input Protocols . . . . . . . . . . . . . . . .   8
     7.2.  Registration  . . . . . . . . . . . . . . . . . . . . . .   8
     7.3.  WHOIS . . . . . . . . . . . . . . . . . . . . . . . . . .   8
   8.  Replay Protection . . . . . . . . . . . . . . . . . . . . . .   9
   9.  Relationship to Existing Standards  . . . . . . . . . . . . .   9
     9.1.  ANS — Agent Name Service  . . . . . . . . . . . . . . . .   9
     9.2.  DNS-AID . . . . . . . . . . . . . . . . . . . . . . . . .   9
     9.3.  W3C DID . . . . . . . . . . . . . . . . . . . . . . . . .   9
     9.4.  x402 and L402 . . . . . . . . . . . . . . . . . . . . . .   9
     9.5.  Google A2A Protocol . . . . . . . . . . . . . . . . . . .  10
     9.6.  OpenAPI . . . . . . . . . . . . . . . . . . . . . . . . .  10
   10. Fee Model Principles  . . . . . . . . . . . . . . . . . . . .  10
   11. Security Considerations . . . . . . . . . . . . . . . . . . .  10
     11.1.  Payment Verification . . . . . . . . . . . . . . . . . .  10
     11.2.  Replay Protection  . . . . . . . . . . . . . . . . . . .  10
     11.3.  Identity Verification  . . . . . . . . . . . . . . . . .  11
     11.4.  Man-in-the-Middle  . . . . . . . . . . . . . . . . . . .  11
   12. Reference Implementation  . . . . . . . . . . . . . . . . . .  11
   13. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  11
   14. References  . . . . . . . . . . . . . . . . . . . . . . . . .  12
     14.1.  Normative References . . . . . . . . . . . . . . . . . .  12
     14.2.  Informative References . . . . . . . . . . . . . . . . .  12
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  12








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1.  Introduction

   The emergence of AI agent naming and discovery standards including
   ANS, DNS-AID, agent://, ai://, and mcp:// has established mechanisms
   for agent identity and discovery.  However, none of these standards
   define how to:

   a.  Execute a task against a discovered agent

   b.  Pay for agent execution in a standardized way

   c.  Verify payment cryptographically before execution

   d.  Receive a verifiable execution receipt

   e.  Prevent replay attacks on payment transactions

   AEPP fills this gap.  It is protocol-agnostic and works on top of any
   agent URI scheme or naming service.  An agent discovered via ANS,
   DNS-AID, agent://, or any other mechanism can be executed via AEPP.

   AEPP is designed to be:

   *  Fee-free per agent — no per-registration or per-naming fees

   *  Open — any agent network may implement AEPP

   *  Federated — no central execution authority

   *  Verifiable — all payments cryptographically verified on-chain

   *  Interoperable — works with all existing agent standards

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119.

   Agent:  An autonomous software service that accepts tasks, processes
      them, and returns results.

   Executor:  The client initiating an agent task execution.

   Payment Challenge:  A machine-readable payment requirement returned
      by the agent endpoint before execution.

   Execution Receipt:  A cryptographically verifiable record of task



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      completion and payment.

   Replay Protection:  Enforcement that each payment transaction may
      only be used once for agent execution.

3.  Protocol Overview

   AEPP defines a three-phase execution model:

   Phase 1 — DISCOVERY
     Client sends GET to agent endpoint
     Agent returns 402 Payment Required + payment challenge

   Phase 2 — PAYMENT
     Client satisfies payment challenge
     Client obtains cryptographic payment proof (transaction hash)

   Phase 3 — EXECUTION
     Client sends POST with task + payment proof
     Agent verifies payment on-chain
     Agent executes task
     Agent returns result + execution receipt

4.  Phase 1 — Discovery

4.1.  Request

   GET https://{agent-endpoint}/?id={agent_id}
   Accept: application/json

4.2.  Response

   The agent MUST return HTTP 402 Payment Required with a payment
   challenge in both the response body and the PAYMENT-REQUIRED header
   (base64 encoded).
















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   HTTP/1.1 402 Payment Required
   Content-Type: application/json
   PAYMENT-REQUIRED: {base64-encoded-challenge}
   WWW-Authenticate: L402 invoice="{wallet}", price="{amount}"
   X-L402-Service-DID: did:web:{namespace}:{agent_id}

   {
     "x402Version": 2,
     "error": "Payment required",
     "resource": {
       "url": "https://{endpoint}/?id={agent_id}",
       "description": "{agent capability}",
       "mimeType": "application/json"
     },
     "accepts": [{
       "scheme": "exact",
       "network": "eip155:8453",
       "amount": "25000",
       "asset": "0x833589fcd6edb6e08f4c7c32d4f71b54bda02913",
       "payTo": "{agent-wallet-address}",
       "maxTimeoutSeconds": 60
     }],
     "agent": {
       "id": "{agent_id}",
       "name": "{agent name}",
       "did": "did:web:{namespace}:{agent_id}",
       "price_usdc": 0.025
     }
   }

5.  Phase 2 — Payment

   The executor satisfies the payment challenge using any compatible
   payment method.  The reference implementation uses USDC on Base
   mainnet (eip155:8453).

   AEPP does not mandate a specific payment network or currency.
   Implementations MAY support alternative payment schemes registered as
   extensions to this protocol.

   The payment proof MUST be a cryptographically verifiable transaction
   identifier that the agent can independently verify against the
   payment network.

5.1.  Reference Payment Implementation






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   Network:  Base Mainnet (eip155:8453)
   Currency: USDC
   Contract: 0x833589fcd6edb6e08f4c7c32d4f71b54bda02913
   Amount:   As specified in payment challenge
   Method:   ERC-20 transfer to agent wallet address
   Proof:    Transaction hash from payment network

5.2.  Autonomous Payment Example

   // Read payment details from challenge
   const challenge = JSON.parse(
     Buffer.from(
       response.headers.get("PAYMENT-REQUIRED"),
       "base64"
     ).toString()
   );
   const { payTo, amount, asset } = challenge.accepts[0];

   // Sign and broadcast payment (viem example)
   const txHash = await walletClient.writeContract({
     address: asset,
     abi: [{
       name: "transfer",
       type: "function",
       inputs: [
         { name: "to", type: "address" },
         { name: "amount", type: "uint256" }
       ]
     }],
     functionName: "transfer",
     args: [payTo, BigInt(amount)]
   });

6.  Phase 3 — Execution

6.1.  Request

   POST https://{agent-endpoint}/?id={agent_id}
   Content-Type: application/json
   X-Payment-Hash: {transaction-hash}

   {
     "prompt": "task description or question"
   }







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6.2.  Payment Verification

   Upon receiving the execution request the agent MUST:

   1.  Extract the payment proof from X-Payment-Hash header

   2.  Verify the transaction exists on the payment network

   3.  Verify the transaction recipient matches the agent wallet

   4.  Verify the transaction amount meets the required amount

   5.  Verify the transaction hash has not been used previously (replay
       protection)

   6.  Record the transaction hash as used before execution

   If any verification step fails the agent MUST return HTTP 403
   Forbidden.

6.3.  Response

   HTTP/1.1 200 OK
   Content-Type: application/json

   {
     "id": "did:web:{namespace}:{agent_id}",
     "result": "{agent response}",
     "receipt": {
       "protocol": "AEPP/1.0",
       "currency": "USDC",
       "amount": 0.025,
       "chain": "eip155:8453",
       "tx": "{transaction-hash}",
       "agent_did": "did:web:{namespace}:{agent_id}",
       "verified_at": "{ISO-8601-timestamp}"
     }
   }

7.  Universal Clip

   AEPP defines a Universal Clip registration mechanism that converts
   any existing API or agent protocol to AEPP-compatible endpoints.
   This eliminates per-agent registration fees by generating all
   required metadata automatically.






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7.1.  Supported Input Protocols

   *  REST APIs — any JSON HTTP endpoint

   *  Model Context Protocol (MCP)

   *  OpenAI plugin manifest

   *  LangChain tools

   *  Google A2A protocol

   *  ANS registered agents

   *  DNS-AID discovered agents

7.2.  Registration

   Any service registers with a single POST request:

POST https://a2a.agentir.com/ans/register
Content-Type: application/json

{
  "name": "Service Name",
  "endpoint": "https://api.example.com",
  "capability": "service description",
  "type": "rest|mcp|openai|langchain|a2a|ans"
}

Response:
{
  "did": "did:web:a2a.agentir.com:{agent_id}",
  "endpoint": "https://a2a.agentir.com/?id={agent_id}",
  "openapi": "https://a2a.agentir.com/openapi.json?id={agent_id}",
  "agent_card": "https://a2a.agentir.com/.well-known/agent.json?id={agent_id}",
  "aepp": "AEPP/1.0 ready",
  "fee": "0.00 per registration"
}

   Registration is free.  AEPP implementations MUST NOT charge per-agent
   registration fees.  Revenue models MUST be based on execution, not
   naming or registration.

7.3.  WHOIS

   Any registered agent is queryable via WHOIS:




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   GET https://a2a.agentir.com/whois?id={agent_id}
   GET https://a2a.agentir.com/whois?did=did:web:a2a.agentir.com:{id}

   Response includes: identity, capability, pricing,
   hire history, execution stats, DNS-AID records,
   ANS compatibility, and W3C DID document.

8.  Replay Protection

   AEPP implementations MUST enforce replay protection.  Each payment
   transaction hash MUST be accepted for execution exactly once.
   Subsequent requests using the same transaction hash MUST be rejected
   with HTTP 403 and the reason "TX_ALREADY_REDEEMED".

   Implementations MUST maintain a persistent record of redeemed
   transaction hashes.  This record MUST survive service restarts.

9.  Relationship to Existing Standards

9.1.  ANS — Agent Name Service

   ANS provides agent identity and naming via DNS and PKI.  AEPP
   provides the execution and payment layer that ANS does not define.
   An ANS-registered agent MAY expose an AEPP-compatible endpoint.  AEPP
   complements ANS without replacing it.

9.2.  DNS-AID

   DNS-AID provides agent discovery via DNS records.  AEPP provides
   execution once an agent is discovered via DNS-AID.  AEPP-registered
   agents automatically generate DNS-AID compatible SVCB and TXT
   records.

9.3.  W3C DID

   Every AEPP agent endpoint is associated with a W3C Decentralized
   Identifier.  The DID document is resolvable at the agent's .well-
   known endpoint.  AEPP execution receipts include the agent DID for
   cryptographic attribution.

9.4.  x402 and L402

   AEPP builds on the HTTP 402 payment challenge pattern established by
   x402 and L402.  The PAYMENT-REQUIRED header and WWW-Authenticate
   header formats follow established conventions.  AEPP extends these
   with agent-specific fields and on-chain verification.





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9.5.  Google A2A Protocol

   The Google Agent-to-Agent (A2A) protocol defines agent communication
   patterns.  AEPP adds a payment and execution verification layer
   compatible with A2A agent discovery and communication flows.

9.6.  OpenAPI

   Every AEPP-registered agent automatically generates an OpenAPI 3.1.0
   specification from capability metadata.  The spec includes x402 as a
   security scheme definition.

10.  Fee Model Principles

   AEPP establishes the following principles for agent execution fee
   models:

   1.  Registration MUST be free.  No per-agent naming or registration
       fees shall be required.

   2.  Discovery MUST be free.  Agent search and capability lookup shall
       not require payment.

   3.  Execution MAY require payment.  Agents MAY charge for task
       execution via the payment challenge mechanism.

   4.  Payment terms MUST be machine-readable.  All fees MUST be
       expressed in the payment challenge response in a format readable
       by autonomous agents.

   5.  Payment MUST be direct.  Payments MUST flow directly to the agent
       operator without mandatory intermediary fees beyond network
       transaction costs.

11.  Security Considerations

11.1.  Payment Verification

   All payments MUST be verified on-chain before execution.  Agents MUST
   NOT execute tasks based on unverified payment claims.  Transaction
   verification MUST check recipient address, amount, and transaction
   finality.

11.2.  Replay Protection

   Transaction hashes are single-use.  Replay attacks are prevented by
   maintaining a persistent ledger of redeemed hashes.  See Section 7
   for requirements.



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11.3.  Identity Verification

   Agent identity is anchored to W3C DIDs with blockchain account
   verification.  Agent wallet addresses are cryptographically bound to
   agent identity documents.

11.4.  Man-in-the-Middle

   All AEPP endpoints MUST use TLS.  Payment challenges MUST include the
   exact recipient wallet address.  Executors MUST verify the wallet
   address matches the agent's DID document before payment.

12.  Reference Implementation

   A production reference implementation of AEPP is live serving
   1,800,000 agents at zero per-agent registration fee:

   Gateway:       https://a2a.agentir.com
   Registration:  https://a2a.agentir.com/ans/register
   Resolution:    https://a2a.agentir.com/ans/resolve
   WHOIS:         https://a2a.agentir.com/whois
   OpenAPI:       https://a2a.agentir.com/openapi.json
   Discovery:     https://a2a.agentir.com/.well-known/ai-plugin.json
   Search:        https://a2a.agentir.com/search?q={query}
   CLI:           npx agentir (npm registry)

   Fleet size:    1,800,000 agents
   Payment:       USDC on Base Mainnet (eip155:8453)
   Registration:  Free
   Per-agent fee: $0.00

   The implementation demonstrates all AEPP phases including Universal
   Clip translation, on-chain payment verification, replay protection,
   W3C DID per agent, ANS and DNS-AID compatibility, semantic vector
   search, and persistent cross-device agent memory.

13.  IANA Considerations

   This document requests registration of the following HTTP header
   fields:

   *  PAYMENT-REQUIRED — base64 encoded payment challenge

   *  X-Payment-Hash — payment transaction proof

   *  X-L402-Service-DID — agent DID for L402 flows





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   This document requests registration of the AEPP protocol identifier
   in the appropriate IANA registry.

14.  References

14.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", RFC 2119, March 1997,
              <https://www.rfc-editor.org/rfc/rfc2119>.

   [RFC7595]  Thaler, D., Hansen, T., and T. Hardie, "Guidelines and
              Registration Procedures for URI Schemes", RFC 7595, June
              2015, <https://www.rfc-editor.org/rfc/rfc7595>.

   [RFC9110]  Fielding, R., Nottingham, M., and J. Reschke, "HTTP
              Semantics", RFC 9110, June 2022,
              <https://www.rfc-editor.org/rfc/rfc9110>.

14.2.  Informative References

   [A2A]      Agentir Network, "Agent Execution and Payment Protocol
              Reference Implementation", 2026,
              <https://a2a.agentir.com>.

   [AEPP-CLI] Agentir Network, "Agentir CLI — AEPP Reference Client",
              2026, <https://www.npmjs.com/package/agentir>.

   [ANS]      GoDaddy Inc., "Agent Name Service", May 2026.

   [DNS-AID]  Mozley, J. and N. Williams, "DNS for AI Discovery", March
              2026, <https://datatracker.ietf.org/doc/draft-
              mozleywilliams-dnsop-dnsaid/>.

   [W3C-DID]  W3C, "Decentralized Identifiers (DIDs) v1.0", 2022,
              <https://www.w3.org/TR/did-core/>.

   [x402]     x402.org, "HTTP 402 Payment Protocol", 2026,
              <https://x402.org>.

Author's Address

   Edward Spink
   Agentir Network
   Email: support@agentir.com
   URI:   https://agentir.com





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