3 releases

0.1.3 Aug 17, 2021
0.1.2 Aug 17, 2021
0.1.0 Jul 20, 2021

MIT license

984 lines


⚠️ This project is heavily work-in-progress and not ready for production => API breakage expected!

Gekko offers utilities to parse substrate metadata, generate the corresponding Rust interfaces, create transactions and the ability to encode/decode those transaction.

The project is split into multiple crates, although all functionality can be exposed by just using gekko.

  • gekko - Contains runtime interfaces to interact with Kusama, Polkadot and Westend, including creating transactions.
  • gekko-metadata - Utilities to parse and process substrate metadata.
    • Can also be enabled in gekko with the "metadata" feature.
  • gekko-generator - Macro to generate Rust interfaces during compile time based on the the parsed substrate metadata.
    • Can also be enabled in gekko with the "generator" feature.

Interacting with the runtime

Gekko exposes multiple interfaces to interact with Kusama/Polkadot, such as extrinsics, storage entires, events, constants and errors.

Disclaimer about types

This library makes no assumptions about parameter types and must be specified manually as generic types. Each field contains a type description which can serve as a hint on what type is being expected, as provided by the runtime meatadata. See the [common] module for common types which can be used.


Transactions can be created by using a transaction builder from the [transaction] module. The transaction formats are versioned, reflecting the changes during Substrates history. Unless you're working with historic data, you probably want the latest version.

Extrinsics can chosen from the [runtime] module and constructed accordingly. Take a look at the [common] module which contains utilities for creating transaction.


use gekko::common::*;
use gekko::transaction::*;
use gekko::runtime::polkadot::extrinsics::balances::TransferKeepAlive;

// In this example, a random key is generated. You probably want to *import* one.
let (keypair, _) = KeyPairBuilder::<Sr25519>::generate();
let currency = BalanceBuilder::new(Currency::Polkadot);

// The destination address.
let destination =

// Send 50 DOT to the destination.
let call = TransferKeepAlive {
    dest: destination,
    value: currency.balance(50),

// Transaction fee.
let payment = currency.balance_as_metric(Metric::Milli, 10).unwrap();

// Build the final transaction.
let transaction: PolkadotSignedExtrinsic<_> = SignedTransactionBuilder::new()

Parsing Metadata

Gekko offers utilities that allow you to search for specific extrinsics or to iterate through all of those.


use gekko::metadata::*;

// Parse runtime metadata
let content = std::fs::read_to_string("metadata_kusama_9080.hex").unwrap();
let data = parse_hex_metadata(content).unwrap().into_inner();

// Get information about the extrinsic.
let extr = data
    .find_module_extrinsic("Balances", "transfer_keep_alive")

assert_eq!(extr.module_id, 4);
assert_eq!(extr.dispatch_id, 3);
        ("dest", "<T::Lookup as StaticLookup>::Source"),
        ("value", "Compact<T::Balance>"),

A macro available in gekko::generator will parse the metadata automatically for you and generate the Rust interfaces at compile time.

License: MIT


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