Practical Error Handling with fp-ts

Practical Error Handling with fp-ts is a skill for Claude Code, Codex from whatiskadudoing/fp-ts-skills. It costs 27 tokens per session (5,903 once invoked), scanned A, original, no licence file.

A guide to treating errors as values instead of throwing exceptions, using fp-ts types such as Either and TaskEither. TaskEither represents an asynchronous operation that can succeed or fail.

In plain words
What is it for?
Use it when writing TypeScript functions that may fail, especially asynchronous operations such as requests or data processing.
Why use it?
It makes failure paths visible in the code and can make error handling more predictable than throwing errors throughout an application.

Skill for Claude CodeCodex

Which agent this was written for is unclear — body not stored (licence); the path alone says nothing.

Good fit Use it when writing TypeScript functions that may fail, especially asynchronous operations…

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Install with agentmods
npx agentmods add skills/whatiskadudoing/fp-ts-skills/fp-errors
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add whatiskadudoing/fp-ts-skills --skill fp-errors
Clone the repo
git clone --depth 1 https://github.com/whatiskadudoing/fp-ts-skills

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for Practical Error Handling with fp-ts

README.md
[![agentmods](https://agentmods.dev/badge/skills/whatiskadudoing/fp-ts-skills/fp-errors.svg)](https://agentmods.dev/skills/whatiskadudoing/fp-ts-skills/fp-errors)
Your own site
<a href="https://agentmods.dev/skills/whatiskadudoing/fp-ts-skills/fp-errors"><img src="https://agentmods.dev/badge/skills/whatiskadudoing/fp-ts-skills/fp-errors.svg" alt="Measured on agentmods" height="20"></a>
Per session 27 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 5,903 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe.
Origin unknown No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00027 $0.05903
Opus 5 $0.00014 $0.02951
Sonnet 5 $0.00005 $0.01181
Haiku 4.5 $0.00003 $0.00590

Measured 7d ago against content hash 2b00309816af, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

Practical Error Handling with fp-ts scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 7d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

() => fetch(url).then(r => r.json()),
skills/fp-errors/SKILL.md · 858 lines

The source is not reproduced here

No licence file

A repository with no LICENSE is all rights reserved by default, so the body is not copied here. The metadata, the measurements and the link are.

Read it on GitHub

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 7d ago First seen · 858 lines · 27 tokens per session scan A 2b00309816af

Subscribe to this mod's changes

Practical Error Handling with fp-ts is a skill published in the GitHub repository whatiskadudoing/fp-ts-skills (11 stars, last pushed 7mo ago), with no licence file. It adds 27 tokens to every session and 5,903 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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