tx402 MCP server

tx402

Plain-English explanations of Algorand transactions, sold as a pay-per-call API with x402 on Algorand.

Live service:

https://tx402-production.up.railway.app

Explain one transaction, every leg of an atomic group, a batch of IDs, or recent account activity. Responses include scaled amounts, inner transactions, asset names, fees, timestamps, counterparties, and source-verified protocol labels.

Try the free fixed-transaction demo without a wallet:

https://tx402-production.up.railway.app/demo?example=algo

GET /explain?txid=YRSG7IKDPCK4XMKFFTFFFYMIHF6SJOMHUOIE4FFUWNLEQ4WG2ZOQ

Example response after payment:

{
  "txid": "YRSG7IKDPCK4XMKFFTFFFYMIHF6SJOMHUOIE4FFUWNLEQ4WG2ZOQ",
  "network": "mainnet",
  "summary": "On June 16, 2019, wallet VCINCV...JPMIPM sent 1 ALGO to CRBMB5...QLXZOY. Paid 0.001 ALGO in fees.",
  "details": {
    "type": "pay",
    "sender": "VCINCVUX2DBKQ6WP63NOGPEAQAYGHGSGQX7TSH4M5LI5NBPVAGIHJPMIPM",
    "transfer": {
      "amount": "1",
      "assetId": 0,
      "unit": "ALGO"
    }
  }
}

Raw Algorand indexer JSON is optimized for machines doing bookkeeping: amounts are base units, assets are numeric IDs, and notes are base64. tx402 is the translation layer for agents and applications that need to explain a transaction to a person.

API

Public routes:

• GET / - landing page with service metadata links
• GET /health - process liveness
• GET /health?deep=1&network=mainnet - readiness check for upstream services
• GET /discovery - machine-readable service description and pricing metadata
• GET /openapi.json - OpenAPI 3.1 specification
• GET /.well-known/agent.json - agent marketplace manifest
• GET /.well-known/x402 - x402 resource manifest
• GET /llms.txt - agent-readable documentation
• GET /demo?example=algo|usdc - free allowlisted Mainnet examples
• GET /explain?txid=...&network=mainnet - paid transaction explanation
• GET /group?txid=...&network=mainnet - paid atomic-group explanation
• POST /batch - paid batch of 1 to 10 transaction IDs

Default prices are $0.005 for /explain, $0.01 for /group, $0.02 for /batch, and $0.01 for /account/activity. Production accepts Mainnet USDC:

• network: algorand:wGHE2Pwdvd7S12BL5FaOP20EGYesN73ktiC1qzkkit8=
• asset: 31566704
• receiver: 6RK3U3OF2B4Q773L4KC7OVFHQGU5I74NHRZ36QN6CVF527CKXAL62YR754

Architecture

tx402 has a small deterministic core and a thin serving shell.

Core:

normalized transaction object.

• src/decoder.js converts raw Algorand indexer JSON into a

readable sentence.

• src/narrator.js converts that normalized object into one

single, group, batch, and account products.

• src/insights.js builds group and account-level summaries.
• src/explainer.js resolves assets and orchestrates the

labels with a verification source for every narrated protocol claim.

• src/knownApps.js maps known app and asset IDs to human

Serving shell:

rate limits, health checks, and graceful shutdown.

• src/index.js owns HTTP routes, middleware ordering, logging,

public indexer.

• src/indexer.js is the only module that talks to AlgoNode's

delegates verification and settlement to the hosted GoPlausible facilitator.

• src/payments.js declares the x402 price and receiver, then

counters without cookies, raw wallet addresses, query strings, or IP history.

• src/rateLimit.js provides the in-memory per-IP limiter.
• src/analytics.js keeps aggregate process-local adoption

Shortened. The full README is on GitHub.