{ "openapi": "3.1.1", "info": { "title": "Transaction Decoder API", "version": "1.0.0", "summary": "See what an EVM transaction actually did: call, events, token transfers, fee, finality.", "description": "Every endpoint performs the same calculation as the human page and returns inputs, result, units, assumptions, sources, warnings and computedAt. MCP endpoint: /mcp." }, "servers": [ { "url": "https://transactiondecoder.usefulweb.site" } ], "paths": { "/api/v1/calculate": { "post": { "operationId": "calculate", "summary": "See what an EVM transaction actually did: call, events, token transfers, fee, finality.", "description": "Looks up a transaction on Ethereum, Base, Arbitrum, OP Mainnet, Polygon, Avalanche or BNB Chain straight from a public RPC node and decodes it locally: the function called (from the verified ABI on Sourcify, a built-in table or the signature database), every event log, ERC-20 token transfers with symbols and decimals, gas fee, status and finality. Works offline for raw calldata too.\n\nMethodology:\n- Raw data comes from public JSON-RPC nodes: eth_getTransactionByHash, eth_getTransactionReceipt, eth_getBlockByNumber (timestamp, \"finalized\" tag) and eth_blockNumber.\n- Function: the first 4 bytes (selector) are matched against, in order, your signature/ABI, the verified ABI of the called contract on Sourcify, a built-in table of common functions, then the Sourcify signature database. The first candidate that ABI-decodes cleanly is used; other candidates are listed (selector collisions exist).\n- Events: topic0 is matched the same way. Without a verified ABI, the first (topics − 1) parameters are assumed to be indexed (flagged as indexingAssumed).\n- Token transfers: Transfer(address,address,uint256) logs with exactly 3 topics (ERC-20; ERC-721 has 4); symbol() and decimals() are read with eth_call.\n- Fake-token check: transfers of a token whose symbol is USDT/USDC/WETH/DAI but whose contract is not the official one on that chain are flagged.\n- Finality: \"finalized\" if the block is at or below the chain's \"finalized\" block tag; otherwise \"unfinalized\" with the confirmation count; \"unknown\" if the node does not support the tag.", "tags": [ "web3" ], "x-mcp-tool": "transaction_decoder", "requestBody": { "required": true, "content": { "application/json": { "schema": { "$ref": "#/components/schemas/TransactionDecoderInput" }, "examples": { "example1": { "summary": "Decode an ERC-20 transfer (offline)", "value": { "mode": "calldata", "chain": "ethereum", "calldata": "0xa9059cbb0000000000000000000000005aaeb6053f3e94c9b9a09f33669435e7ef1beaed00000000000000000000000000000000000000000000000000000000004c4b40" } }, "example2": { "summary": "Custom signature with a tuple (offline)", "value": { "mode": "calldata", "chain": "base", "signature": "setConfig((address,uint256,bool),string)", "calldata": "0xc48cfc700000000000000000000000005aaeb6053f3e94c9b9a09f33669435e7ef1beaed000000000000000000000000000000000000000000000000000000000000002a0000000000000000000000000000000000000000000000000000000000000001000000000000000000000000000000000000000000000000000000000000008000000000000000000000000000000000000000000000000000000000000000056869676821000000000000000000000000000000000000000000000000000000" } } } } } }, "responses": { "200": { "description": "Calculation result envelope.", "content": { "application/json": { "schema": { "$ref": "#/components/schemas/TransactionDecoderResult" } } } }, "400": { "description": "Malformed JSON body.", "content": { "application/problem+json": { "schema": { "$ref": "#/components/schemas/Problem" } } } }, "422": { "description": "Invalid input (see errors[]).", "content": { "application/problem+json": { "schema": { "$ref": "#/components/schemas/Problem" } } } }, "429": { "description": "Rate limit exceeded (see Retry-After).", "content": { "application/problem+json": { "schema": { "$ref": "#/components/schemas/Problem" } } } } } } }, "/api/v1/tool": { "get": { "operationId": "getToolDefinition", "summary": "Inputs, output schema and examples for this tool", "responses": { "200": { "description": "Tool definition.", "content": { "application/json": { "schema": { "type": "object" } } } } } } } }, "components": { "schemas": { "Problem": { "type": "object", "description": "RFC 9457 problem details. 422 responses include per-field `errors`.", "required": [ "type", "title", "status", "detail" ], "properties": { "type": { "type": "string" }, "title": { "type": "string" }, "status": { "type": "integer" }, "detail": { "type": "string" }, "code": { "type": "string" }, "errors": { "type": "array", "items": { "type": "object", "required": [ "field", "message" ], "properties": { "field": { "type": "string" }, "message": { "type": "string" } } } } } }, "TransactionDecoderInput": { "type": "object", "additionalProperties": false, "properties": { "mode": { "title": "What do you have?", "type": "string", "enum": [ "lookup", "calldata" ], "default": "lookup" }, "chain": { "title": "Chain", "type": "string", "enum": [ "ethereum", "base", "arbitrum", "optimism", "polygon", "avalanche", "bsc" ], "default": "ethereum" }, "txHash": { "title": "Transaction hash", "type": "string", "maxLength": 66 }, "calldata": { "title": "Calldata (input data)", "type": "string", "maxLength": 200000 }, "signature": { "title": "Function signature (optional)", "type": "string", "maxLength": 500 }, "abi": { "title": "Contract ABI JSON (optional)", "type": "string", "maxLength": 500000 } }, "required": [] }, "TransactionDecoderResult": { "type": "object", "additionalProperties": false, "required": [ "schemaVersion", "tool", "computedAt", "inputs", "summary", "result", "units", "assumptions", "sources", "warnings", "presentation", "links" ], "properties": { "schemaVersion": { "type": "string", "const": "1.0" }, "tool": { "type": "object", "additionalProperties": false, "required": [ "id", "name", "version" ], "properties": { "id": { "type": "string" }, "name": { "type": "string" }, "version": { "type": "string" } } }, "computedAt": { "type": "string", "format": "date-time" }, "inputs": { "type": "object", "description": "Normalised inputs actually used, including applied defaults." }, "summary": { "type": "string" }, "result": { "type": "object", "additionalProperties": false, "required": [ "mode", "chain", "transaction", "call", "logs", "tokenTransfers", "graph" ], "properties": { "mode": { "type": "string", "enum": [ "lookup", "calldata" ] }, "chain": { "type": "object", "additionalProperties": false, "required": [ "id", "name", "chainId" ], "properties": { "id": { "type": "string" }, "name": { "type": "string" }, "chainId": { "type": "integer" } } }, "transaction": { "type": [ "object", "null" ], "additionalProperties": false, "required": [ "hash", "status", "finality", "blockNumber", "timestamp", "confirmations", "from", "to", "contractCreated", "valueWei", "value", "gasUsed", "effectiveGasPriceWei", "feeWei", "fee", "nonce", "type" ], "properties": { "hash": { "type": "string" }, "status": { "type": "string", "enum": [ "success", "reverted", "pending" ] }, "finality": { "type": "string", "enum": [ "pending", "unfinalized", "finalized", "unknown" ] }, "blockNumber": { "type": [ "integer", "null" ] }, "timestamp": { "type": [ "string", "null" ] }, "confirmations": { "type": [ "integer", "null" ] }, "from": { "type": "string" }, "to": { "type": [ "string", "null" ] }, "contractCreated": { "type": [ "string", "null" ] }, "valueWei": { "type": "string" }, "value": { "type": "string" }, "gasUsed": { "type": [ "string", "null" ] }, "effectiveGasPriceWei": { "type": [ "string", "null" ] }, "feeWei": { "type": [ "string", "null" ] }, "fee": { "type": [ "string", "null" ] }, "nonce": { "type": "integer" }, "type": { "type": "integer" } } }, "call": { "type": [ "object", "null" ], "additionalProperties": false, "required": [ "selector", "signature", "signatureSource", "args", "alternatives" ], "properties": { "selector": { "type": "string" }, "signature": { "type": [ "string", "null" ] }, "signatureSource": { "type": [ "string", "null" ] }, "alternatives": { "type": "array", "items": { "type": "string" } }, "args": { "type": "array", "items": { "type": "object", "additionalProperties": false, "required": [ "name", "type", "value" ], "properties": { "name": { "type": "string" }, "type": { "type": "string" }, "value": { "type": "string" } } } } } }, "logs": { "type": "array", "items": { "type": "object", "additionalProperties": false, "required": [ "index", "address", "topic0", "event", "eventSource", "indexingAssumed", "args" ], "properties": { "index": { "type": "integer" }, "address": { "type": "string" }, "topic0": { "type": [ "string", "null" ] }, "event": { "type": [ "string", "null" ] }, "eventSource": { "type": [ "string", "null" ] }, "indexingAssumed": { "type": "boolean" }, "args": { "type": "array", "items": { "type": "object", "additionalProperties": false, "required": [ "name", "type", "indexed", "value" ], "properties": { "name": { "type": "string" }, "type": { "type": "string" }, "indexed": { "type": "boolean" }, "value": { "type": "string" } } } } } } }, "tokenTransfers": { "type": "array", "items": { "type": "object", "additionalProperties": false, "required": [ "token", "symbol", "from", "to", "raw", "amount" ], "properties": { "token": { "type": "string" }, "symbol": { "type": [ "string", "null" ] }, "from": { "type": "string" }, "to": { "type": "string" }, "raw": { "type": "string" }, "amount": { "type": [ "string", "null" ] } } } }, "graph": { "type": "object", "additionalProperties": false, "required": [ "nodes", "edges" ], "properties": { "nodes": { "type": "array", "items": { "type": "object", "additionalProperties": false, "required": [ "id", "kind", "label" ], "properties": { "id": { "type": "string" }, "kind": { "type": "string" }, "label": { "type": "string" } } } }, "edges": { "type": "array", "items": { "type": "object", "additionalProperties": false, "required": [ "from", "to", "relation" ], "properties": { "from": { "type": "string" }, "to": { "type": "string" }, "relation": { "type": "string" } } } } } } } }, "units": { "type": "object", "additionalProperties": { "type": "string" } }, "assumptions": { "type": "array", "items": { "type": "string" } }, "sources": { "type": "array", "items": { "type": "object", "additionalProperties": false, "required": [ "title" ], "properties": { "title": { "type": "string" }, "url": { "type": "string" }, "publisher": { "type": "string" }, "retrievedAt": { "type": "string" }, "note": { "type": "string" } } } }, "warnings": { "type": "array", "items": { "type": "string" } }, "presentation": { "type": "array", "items": { "type": "object" }, "description": "Display blocks used by the human page (same data)." }, "links": { "type": "object", "additionalProperties": false, "required": [ "human", "api", "openapi", "methodology" ], "properties": { "human": { "type": "string", "format": "uri" }, "api": { "type": "string", "format": "uri" }, "openapi": { "type": "string", "format": "uri" }, "methodology": { "type": "string", "format": "uri" } } } } } } } }