BTSL (Bitcoin Transaction Schema Language): A Declarative Validation Schema for PSBT Workflows

A new tool, a client-side playground for the Maker pipeline as described in the BTSL v1.0 specification, has been recently made available to the public. This development offers users an interactive environment where they can engage directly with the process of constructing Bitcoin transactions according to the specified schema. The playground is accessible through a live demo hosted at https://btsl-playground.vercel.app/, with its source code available on GitHub at github.com/tsua0002/btsl-playground. The platform facilitates a step-by-step guide through the entire transaction creation process, beginning with Schema Input and continuing through Parameter Binding, Code Generation, and finally outputting a Partially Signed Bitcoin Transaction (PSBT).

One of the most notable features of this playground is its ability to run entirely in the browser without requiring a server or handling private keys, thereby enhancing security and accessibility for users. It comes pre-loaded with examples covering five normative use cases outlined in the specification. These include basic payment transactions using a public key, TRI-COUNT shared settlements, 1-of-2 and 2-of-2 Pay-to-Witness-Script-Hash (P2WSH) multisig arrangements, OP_RETURN data embedding, and timelocked Taproot vault workflows that depend on other conditions.

Furthermore, the tool allows for the binding of parameters against live mainnet Unspent Transaction Outputs (UTXOs) using the Blockstream API and real-time fee rates from Mempool.space. Users can then export the constructed transactions as unsigned PSBTs, which are compatible with various signing tools like Sparrow, Coldcard, bitcoin-cli, and other tools supporting the Bitcoin Improvement Proposal 174 standard.

While this release focuses on the Maker side of the transaction construction process, development is ongoing for the Validator pipeline. This upcoming feature aims to introduce Zero-Trust UTXO restoration and independent ASSERT replay, promising an even more robust framework for Bitcoin transaction validation. Feedback from early users, especially regarding the developer experience and any issues encountered while exploring the provided examples, is highly encouraged to refine and enhance the platform's capabilities.