EM-A2A: Agent-to-Agent Payment Protocol

use em-a2a when one agent needs to pay, escrow funds with, check credit scores for, or verify the on-chain identity of another agent on the tron blockchain. this skill handles direct transfers, escrow locking/release/refund, credit lookups, and fee previews. do not use for api endpoint payments (use paybot) or http 402 interception (use x402).

intent

this skill enables trustless peer-to-peer payments between autonomous agents on tron. it supports three payment modes: direct transfer for trusted counterparties, escrow for conditional funding (work completion gates release), and credit/identity checks before transacting. use it anytime agent a needs to compensate agent b for services, compute, or data, or when you need to validate an agent's reputation before sending funds.

inputs

required environment variables

• A2A_NETWORK: tron network identifier. set to shasta for testnet, mainnet for production. defaults to shasta if unset.
• A2A_PRIVATE_KEY: tron private key (64 hex characters) controlling the sender agent's wallet. do not commit to version control. store in secure env or secrets manager.

mcp server dependency

• @poisonpyf/a2a-mcp (npm package). installed via npx in mcp client config. requires node 16+.

skill parameters (per-call)

• agentId: did:bai:tron: format agent identifier (credit/identity checks)
• from: sender did:bai:tron: wallet address
• to: recipient did:bai:tron: wallet address
• amount: transfer amount in smallest unit (6 decimals for usdc/usdt, e.g., 1000000 = 1 usdc)
• token: token symbol (usdc, usdt, trx). default usdc.
• action: escrow action (lock, release, refund)
• mode: fee calculation mode (fixed_tier, variable_float)
• memo: optional transaction note (max 255 chars)
• escrowId: returned from prior a2a_escrow lock call

procedure

workflow 1: hiring another agent with escrow (recommended for new counterparties)

1. call a2a_credit(agentId) with target agent's did. parse response for credit score (300-950 range), level (excellent/good/fair/poor/none), and trend. decide whether to proceed based on score threshold.

2. call a2a_revenue(amount, mode="fixed_tier") to preview protocol fee. this returns fee percentage and final deducted amount. confirm fee is acceptable.

3. call a2a_escrow(from, to, amount, action="lock", task="<description>"). this locks funds on-chain and returns escrowId. funds are held in contract, not transferred to recipient yet.

4. agent b (recipient) performs agreed work. both parties monitor completion off-chain or via external trigger.

5. upon work acceptance, call a2a_escrow(from, to, amount, action="release", escrowId). contract releases funds to recipient and auto-updates recipient's credit score upward.

6. on-chain transaction confirms. both agents' credit histories record the transaction. skill execution completes.

edge case: work rejection or dispute. if agent a rejects work, call a2a_escrow(from, to, amount, action="refund", escrowId) before the release deadline (typically 30 days). this returns funds to sender.

workflow 2: direct payment (use for trusted counterparties only)

1. call a2a_credit(agentId) to validate counterparty reputation. confirm score is above your risk threshold.

2. call a2a_revenue(amount, mode) to understand fee structure. choose fixed_tier for volume discounts or variable_float for risk-adjusted pricing.

3. call a2a_pay(from, to, amount, token="USDC", memo). this executes immediate transfer, runs aml screening on-chain, deducts protocol fee, and transfers net amount to recipient. returns tx hash and confirmation.

4. poll tron mainnet or testnet explorer for tx confirmation (typically 3-5 seconds). skill completes once block confirms.

workflow 3: identity verification (optional pre-flight)

1. call a2a_credit(agentId) as in workflows 1 and 2. the response includes on-chain did validation, kya status (kyc-approved / pending / rejected), and leaderboard rank.

2. parse kya status. if rejected or pending, do not send funds until status clears.

3. proceed to payment workflow.

decision points

decision: should i escrow or pay directly?

• if counterparty credit score < 500 (poor/none level), use escrow. never direct pay to unknown agents.
• if score >= 700 (good/excellent), direct payment is acceptable.
• if score 500-700 (fair), use escrow for amounts > $5k USD equivalent. direct pay for smaller amounts.

decision: which fee mode?

• use fixed_tier if transaction amount is stable and you want predictable costs. good for recurring payments.
• use variable_float if counterparty is new or high-risk. higher fee but adjusts down as credit improves over time.

decision: what if the mcp server is offline or a2a_private_key is missing?

• if A2A_PRIVATE_KEY env var is unset or malformed, all calls fail with auth error. manually set the key before retrying. do not proceed without valid credentials.
• if @poisonpyf/a2a-mcp server is unreachable, mcp client will timeout after 10 seconds. check network connectivity and restart mcp server. retry call.

decision: what if tron network is congested?

• testnet (shasta) rarely congests. mainnet can experience 30-120 second delays during high volume. if tx confirmation takes > 2 minutes, resubmit with higher priority fee. check tron grid status dashboard.

decision: what if counterparty disputes an escrow release?

• escrow has a dispute window (typically 7 days post-release). both parties can appeal to protocol arbiters. if unresolved, funds may be frozen pending manual arbitration. plan for 2-4 week resolution.

decision: what if the credit score endpoint returns no data (new agent)?

• if agentId is not yet on-chain, a2a_credit returns score=300 (none level). treat as untrusted. escrow only, no direct pay. as agent builds history, score increases.

output contract

a2a_pay response

{
  "txHash": "0xabc123...",
  "from": "did:bai:tron:TBu...",
  "to": "did:bai:tron:TSa...",
  "amount": "1000000",
  "fee": "10000",
  "netAmount": "990000",
  "token": "USDC",
  "status": "confirmed",
  "blockNumber": 45123456,
  "timestamp": 1699564800
}

a2a_escrow lock response

{
  "escrowId": "esc_xyz789",
  "from": "did:bai:tron:TBu...",
  "to": "did:bai:tron:TSa...",
  "amount": "500000000",
  "status": "locked",
  "task": "Code review",
  "releaseDeadline": 1700169600,
  "txHash": "0xdef456..."
}

a2a_escrow release/refund response

{
  "escrowId": "esc_xyz789",
  "action": "release",
  "status": "confirmed",
  "txHash": "0xghi789...",
  "timestamp": 1699650000
}

a2a_credit response

{
  "agentId": "did:bai:tron:TSa...",
  "score": 725,
  "level": "good",
  "trend": "up",
  "kyaStatus": "kyc-approved",
  "leaderboardRank": 142,
  "transactionCount": 47,
  "averageTransactionSize": "250000000",
  "defaultRate": 0.002
}

a2a_revenue response

{
  "amount": "100000000",
  "mode": "fixed_tier",
  "feePercentage": 0.01,
  "feeAmount": "1000000",
  "netAmount": "99000000"
}

outcome signal

the skill worked if:

1. a2a_pay: tx hash is returned with status "confirmed". check tron scanner (https://tronscan.org for mainnet, https://shasta.tronscan.org for testnet) and confirm block number and recipient received amount. wait 3-5 seconds for confirmation.

2. a2a_escrow lock: escrowId is returned. funds disappear from your wallet and appear in escrow contract on-chain. verify on tron scanner by checking contract state.

3. a2a_escrow release: recipient's wallet balance increases by net amount. your credit score updates visibly on leaderboard within 1 minute. recipient's score increases.

4. a2a_credit: score and level are returned. compare to previous call to confirm data freshness. leaderboard rank should match on-chain record.

5. a2a_revenue: fee percentage is returned and matches documented fee schedule for the chosen mode. no funds move; this is a read-only preview.

failure indicators: tx hash is null, status is "pending" after 5 minutes, error message contains "insufficient balance", "invalid agent id", "network timeout", or "aml screening failed". check logs, validate inputs, and retry.

credits: original author undeclared. enriched per implexa standards with explicit decision logic, edge cases, network timeout handling, and output contracts. github source: https://github.com/ypeng1620-beep/EM-A2A