# base-tx-explain

> One MCP tool: explain_transaction(tx_hash) -> strict JSON explanation of any Base mainnet (chain id 8453) transaction. Deterministic onchain decode, no LLM in the response path.

MCP endpoint (streamable HTTP): POST https://base-tx-explain.fly.dev/mcp
Pricing: first 10 calls free per client, then $0.02 per call in USDC on Base via x402 (payment challenge is returned in-band; attach payment at _meta["x402/payment"] and retry). No account, no API key.

## Contracts

- [OpenAPI](https://base-tx-explain.fly.dev/openapi.json): request/response schemas for the tools/call envelope
- [Health](https://base-tx-explain.fly.dev/healthz): liveness and demand counters

## Docs

- [Documentation](https://0200project.com/docs/): request format, field contract, x402 payment loop, self-hosting
- [Site](https://0200project.com/): product overview
- [Source](https://github.com/0200project/base-tx-explain)
- MCP registry name: io.github.0200project/base-tx-explain