About FabTally Decode
FabTally Decode is a paid, read-only MCP server for developers who need to turn EVM logs, calldata, and selectors into human-readable JSON. It also retrieves verified ABIs and resolves proxy implementations across six named chains.
Key features
- 01Decode event logs
- 02Explain function calldata
- 03Look up selectors and topics
- 04Fetch verified ABIs
- 05Resolve proxy implementations
Use cases
- 01Inspect transaction event logs
- 02Interpret contract function calls
- 03Identify a selector or event topic
- 04Retrieve a contract ABI
MCP support
Exposes four paid decoding and ABI tools to MCP clients over stdio or streamable HTTP. Calls can use an x402 payment payload; unpaid calls return a payment challenge.
Configuration
Remote servers need no local install. Pick your client, then copy the config or install in one click.
https://decode.fabtally.com/mcpclaude mcp add --transport http zvmzaretsky-onchain-decode https://decode.fabtally.com/mcp{"mcpServers":{"zvmzaretsky-onchain-decode":{"type":"http","url":"https://decode.fabtally.com/mcp"}}}Open in Cursor{"servers":{"zvmzaretsky-onchain-decode":{"type":"http","url":"https://decode.fabtally.com/mcp"}}}Open in VS Code{"mcpServers":{"zvmzaretsky-onchain-decode":{"type":"http","url":"https://decode.fabtally.com/mcp"}}}{"mcpServers":{"zvmzaretsky-onchain-decode":{"serverUrl":"https://decode.fabtally.com/mcp"}}}Run commands in a terminal; paste JSON into the client’s MCP config and restart. Servers that need sign-in will prompt on first connect.
Tools
4| Parameter | Type | Required | Description |
|---|---|---|---|
| abi | any | No | Optional contract ABI (JSON array or JSON string). If omitted, the ABI is resolved from the verified source (Sourcify/Blockscout) or 4byte.directory. |
| data | string | No | Log data field (0x hex) holding the non-indexed args. |
| chain | enum | Yes | EVM chain: ethereum | base | arbitrum | optimism | polygon | bsc.ethereum | base | arbitrum | optimism | polygon | bsc |
| topics | array | No | Log topics array (topic0 is the event signature hash for non-anonymous events). |
| address | string | No | Contract address of a single log (used with topics + data). |
| tx_hash | string | No | Transaction hash (0x + 64 hex) — decodes every event log in the tx. |
| x_payment | string | No | x402 payment payload (base64) for this PAID decode. If supplied it is forwarded as the X-PAYMENT header to settle the call and return the real result instead of a 402 challenge. Omit to get the price challenge first. |
Details
From the project READMEFabTally Decode — MCP server
Developer on-chain decoding reads that turn raw EVM bytes into human-readable JSON — the capability buried inside $49-999/mo RPC plans. Fronts the Decode HTTP API at https://decode.fabtally.com. Holds no private key.
Tools (all paid; a call with no payment returns the decoded x402 402 challenge)
| Tool | Price | What it does |
|---|---|---|
decode_log | $0.003 | Flagship. Decode event LOGS to JSON. {chain, tx_hash} decodes every log in a tx, or {chain, address, topics[], data} a single log; optional abi. Returns event name + canonical signature + named/typed args — handling tuple/array/nested params, anonymous events, indexed vs non-indexed. Resolves ABI via Sourcify/Blockscout + 4byte when none is given. |
decode_calldata | $0.002 | Decode a function call. {chain, to?, data, abi?} → selector resolved to a function signature (provided ABI / verified source / 4byte.directory) + fully decoded typed arguments. |
selector_lookup | $0.001 | Resolve a 4-byte function selector (0x+8 hex) or a 32-byte event topic (0x+64 hex) to human signature(s) via 4byte.directory + openchain.xyz, with a verified flag. |
abi_fetch | $0.002 | Fetch a contract's verified ABI + metadata (Sourcify/Blockscout) + verification status + full proxy-implementation resolution (EIP-1967/1822/OZ-legacy/beacon) — returns the implementation ABI for proxies. Args: address, chain. |
Chains: ethereum, base, arbitrum, optimism, polygon, bsc.
Every tool also accepts an optional x_payment (base64 x402 payload) that is
forwarded as the X-PAYMENT header to settle the call and return the real result.
Humans can instead prepay by card and use an X-FabTally-Key credit key against
the HTTP API.
Transports
- stdio (portable):
npx fabtally-decode-mcp(bin:fabtally-decode-mcp) - streamable-http (hosted):
https://decode.fabtally.com/mcp
Config: FABTALLY_DECODE_BASE (default https://decode.fabtally.com).
Read-only, keyless, stateless, descriptive. Operated by Sunstone Soft (fabtally.com). Not a security guarantee or financial advice.
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