domain-fintech — Claude Code skill: Rust rules for fintech
A skill that gives the agent fintech domain rules for Rust: decimal money, immutable transactions, audit trails. Useful when you build payments or ledgers.
npx skills add actionbook/rust-skills --skill domain-fintech -a claude-codeWhat domain-fintech does
The skill spells out fintech domain constraints and maps them to Rust decisions. The hard rule: never use f64 for money, since floating point loses precision — reach for rust_decimal::Decimal instead. Transactions have to stay immutable and traceable, which points to Arc<T> and an event-sourced model. Money cannot appear or vanish, so totals get validated through types.
Inside are tables linking domain rule to design constraint to Rust implementation, a crate list (rust_decimal, chrono, time, uuid, serde, validator) and patterns: a currency newtype, event sourcing, structured logging with trace IDs, double-entry debit/credit. There is an Amount example that rejects adding two different currencies, plus a table of common mistakes: f64 for amounts, mutable transactions, amounts stored as strings, silent overflow.
The skill does not write code or pull in crates for you. It sets the frame the agent reasons in, so dependencies like rust_decimal still go into your Cargo.toml by hand. On a non-fintech Rust project those constraints will just get in the agent's way.
What it helps with
- add amounts in different currencies without losing precision
- keep transactions immutable and auditable
- pick a money type instead of f64
- define transaction boundaries through ownership
- set up structured logs with trace IDs for disputed operations
Example prompts for the agent
- design a payment model in Rust following domain-fintech rules
- review my money-handling code for f64 and mutable transactions
- sketch a double-entry ledger on rust_decimal
How to install domain-fintech
1Skills CLI (Vercel)
npx skills add actionbook/rust-skills --skill domain-fintech -a claude-code2Manually: put the files in place
~/.claude/skills/domain-fintech/SKILL.mdCopy the whole skill folder; for one project use .claude/skills/domain-fintech/
1Skills CLI (Vercel)
npx skills add actionbook/rust-skills --skill domain-fintech -a codex2Manually: put the files in place
.agents/skills/domain-fintech/SKILL.mdFor all projects use ~/.agents/skills/
1Skills CLI (Vercel)
npx skills add actionbook/rust-skills --skill domain-fintech -a cursor2Manually: put the files in place
.cursor/skills/domain-fintech/SKILL.mdCursor also reads .agents/skills/ and .claude/skills/
1GitHub CLI
gh skill install actionbook/rust-skills domain-fintech2Manually: put the files in place
.github/skills/domain-fintech/SKILL.md1Skills CLI (Vercel)
npx skills add actionbook/rust-skills --skill domain-fintech -a gemini-cli2Platform CLI
gemini skills install https://github.com/actionbook/rust-skills --path skills/domain-fintechManually: put the files in place
.devin/skills/domain-fintech/SKILL.mdThe legacy .windsurf/skills/ path still works
Skills CLI (Vercel)
npx skills add actionbook/rust-skills --skill domain-fintech -a opencodeClaude.ai
Zip the folder and upload it in Settings → Capabilities → Skills
Step by step, with commands for each platform: How to install skills in Claude Code: five ways
Questions about domain-fintech
How do I install domain-fintech in Claude?
Run npx skills add actionbook/rust-skills --skill domain-fintech -a claude-code. The skill lands in ~/.claude/skills/domain-fintech/SKILL.md.
What does domain-fintech do?
It gives the agent fintech rules for Rust: decimal arithmetic for money, immutable transactions, audit trails and consistent balances.
Do I need to add anything to my project?
Yes. The skill only recommends crates such as rust_decimal; adding them to Cargo.toml is on you.
