---
name: fp-backend
source: https://app.decimal.ai/s/fp-backend@2/SKILL.md
source_sha256: 0963488596c4
---

# fp-ts Backend Patterns

Functional programming patterns for building type-safe, testable backend services using fp-ts.

## Detailed Guide

Read [the detailed guide](references/detailed-guide.md) before executing this skill. It retains the complete procedure and reference material. Treat its safety, prerequisites, and validation requirements as mandatory. For focused work, load the relevant sections; for end-to-end work, read the guide completely.

## When to Use
- You are building or refactoring a Node.js or Deno backend with fp-ts.
- The task involves dependency injection, service composition, or typed backend errors with `ReaderTaskEither`.
- You need functional backend architecture patterns rather than isolated utility snippets.

## Limitations
- Use this skill only when the task clearly matches the scope described above.
- Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
- Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.