mcp-bytesmith

A pure-Python Model Context Protocol server, built on the official MCP SDK (FastMCP), exposing a toolbox of byte-wrangling utilities — encoding, hashing, number crunching, and Ethereum primitives — all computed locally and for real, with no network calls or remote APIs.

Distribution name: mcp-bytesmith · import package: mcp_bytesmith.

Tools

mcp-bytesmith ships an always-on core toolset built entirely on the Python standard library, so it works out of the box with no extra dependencies. This covers the everyday primitives: encode and decode move data between a wide set of schemes (hex, the Base64/Base32 family, Base58/Base58check, Base45, and more), hash computes cryptographic, CRC, and fast non-cryptographic digests, hash_file checksums a file on disk and soft-verifies it against an expected digest, hmac computes and verifies keyed-hash authentication tags, and num_convert translates integers between bases. Rounding out the core are bytes_edit (pad/trim/slice/concat byte glue), data_uri (build and parse data: URIs), otpauth_uri (build and parse otpauth:// authenticator provisioning URIs), unicode_normalize and charset_transcode for text and character-set work, string_escape/string_unescape for JSON/JS/Python/C escaping, codepoints for per-scalar Unicode inspection, random for CSPRNG-backed bytes, tokens, and passphrases, and id_generate for UUIDs (v1/v4/v5/v7), ULIDs, and nanoids. password_hash turns a password into a verifiable storage string and checks one back — scrypt and PBKDF2 out of the box, bcrypt and the argon2 variants with the crypto extra — while derive_key derives raw key bytes from a password or secret via PBKDF2, scrypt, or HKDF.

An opt-in Ethereum/EVM toolset (enabled via the ethereum extra) adds the primitives you reach for when working on-chain: eth_hash for keccak-256, EIP-191, EIP-712 typed-data, and EIP-7702 authorization hashing, eth_userop_hash for the ERC-4337 userOpHash (EntryPoint 0.6/0.7/0.8), abi_codec and rlp_codec for ABI and RLP encode/decode, eth_selector for function and event selectors, abi_inspect for converting a contract ABI between its JSON and human-readable forms and listing every selector and topic0 it declares, eth_calldata for splitting a call's calldata into named, typed arguments (and building it back), eth_log_decode for turning a receipt log's topics and data into named event arguments, eth_revert_decode for turning a failed call's revert data into a reason (Error(string), Panic(uint256), or a custom error), eth_bytecode for disassembling deployed bytecode, scraping the selectors out of its dispatcher, and reading its trailing solc metadata, eth_tx_codec for transactions, eth_storage_slot for storage layout — mapping and array slots, plus the well-known constant ones (EIP-1967 proxy, UUPS, ERC-7201 namespaced, diamond) — eth_address_case for EIP-55 checksums, ens_namehash for EIP-137 ENS namehash/labelhash, bip39 for BIP-39 mnemonic generation, validation, and seed derivation, bip32_derive for BIP-32/44 HD key and address derivation from a seed, eth_eoa_address for the address and public key behind a private key, and eth_contract_address for CREATE and CREATE2 deployment addresses. An always-available info tool reports which toolsets are active along with version information.

An opt-in serialization toolset (enabled via the serialize extra) adds serialize_codec, a single tool multiplexed by format. It encodes and decodes schemaless structured data across CBOR, MessagePack, bencode, and ASN.1 DER/BER (a tag-length-value tree; the crypto extra's asn1crypto is needed for ASN.1); it encodes and decodes SSZ (Simple Serialize) driven by an options.schema, also returning the hash_tree_root; and it decodes raw protobuf wire format (protobuf is decode-only — without a .proto schema it surfaces field numbers, wire types, and values rather than field names).

Further toolsets (the rest of crypto, IDs, validation) are on the roadmap — see TODO.

Development

uv sync                 # create venv + install (incl. dev extras)
uv run mcp-bytesmith    # start the server over stdio
uv run pytest           # run the test suite

Sponsoring

mcp-bytesmith is free, open-source software developed in my spare time. Sponsorships are what keep the project alive and actively maintained — they fund new toolsets, bug fixes, and ongoing support, and they're a direct signal that the work is worth continuing.

If the project is useful to you, please consider sponsoring it through GitHub Sponsors. Click the Sponsor button at the top of the repository, or visit the link directly, and pick a one-time or recurring tier. Every contribution, large or small, is hugely appreciated and goes straight back into keeping mcp-bytesmith healthy.

License

GPLv3 — see LICENSE.

The bundled passphrase wordlist (src/mcp_bytesmith/wordlists/eff_large.txt, used by the random tool's passphrase kind) is the EFF "large" wordlist by the Electronic Frontier Foundation, licensed CC BY 3.0 US.

The bundled BIP-39 wordlist (src/mcp_bytesmith/wordlists/bip39_english.txt, used by the bip39 tool) is the canonical English wordlist from BIP-39, which falls under the MIT License. Its SHA-256 is 2f5eed53a4727b4bf8880d8f3f199efc90e58503646d9ff8eff3a2ed3b24dbda.