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.
npx skills add mpsuesser/pi-effect-harness --skill effect-filesystemgit clone --depth 1 https://github.com/mpsuesser/pi-effect-harnessWrote 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.
[](https://agentmods.dev/skills/mpsuesser/pi-effect-harness/effect-filesystem)<a href="https://agentmods.dev/skills/mpsuesser/pi-effect-harness/effect-filesystem"><img src="https://agentmods.dev/badge/skills/mpsuesser/pi-effect-harness/effect-filesystem.svg" alt="Measured on agentmods" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00025 | $0.03678 |
| Opus 5 | $0.00013 | $0.01839 |
| Sonnet 5 | $0.00005 | $0.00736 |
| Haiku 4.5 | $0.00003 | $0.00368 |
Grade A, and why
effect-filesystem scanned grade A with 0 findings 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.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 620 lines — stays where its author put it; the contents beside it link to each section on GitHub.
FileSystem Platform Abstraction
Use effect FileSystem for platform-abstract file I/O. Stock layers are provided for Node.js and Bun; @effect/platform-browser does not provide a FileSystem layer in beta.74, so browser code needs a custom/injected implementation.
Basic Pattern
import { FileSystem } from 'effect';
import { Effect } from 'effect';
// Service injection via yield*
const program = Effect.gen(function* () {
const fs = yield* FileSystem.FileSystem;
// Use fs methods here
const content = yield* fs.readFileString('path/to/file.txt');
return content;
});
Reading Operations
Read File (Binary)
import { FileSystem } from 'effect';
import { Effect } from 'effect';
const readBinary = Effect.gen(function* () {
const fs = yield* FileSystem.FileSystem;
const bytes = yield* fs.readFile('data.bin');
return bytes; // Uint8Array
});
Read File (String)
import { FileSystem } from 'effect';
import { Effect } from 'effect';
const readText = Effect.gen(function* () {
const fs = yield* FileSystem.FileSystem;
const content = yield* fs.readFileString('config.json');
return content; // string
});
Stream File
import { FileSystem } from 'effect';
import { Effect } from 'effect';
const streamFile = Effect.gen(function* () {
const fs = yield* FileSystem.FileSystem;
// fs.stream() returns a Stream directly — not an Effect
const stream = fs.stream('large-file.log');
return stream; // Stream<Uint8Array, PlatformError>
});
Read Directory
import { FileSystem } from 'effect';
import { Effect } from 'effect';
const listFiles = Effect.gen(function* () {
const fs = yield* FileSystem.FileSystem;
const entries = yield* fs.readDirectory('src/');
return entries; // ReadonlyArray<string>
});
Read Symbolic Link
import { FileSystem } from 'effect';
import { Effect } from 'effect';
const readLink = Effect.gen(function* () {
const fs = yield* FileSystem.FileSystem;
const target = yield* fs.readLink('symlink');
return target; // string
});
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.
- 7d ago First seen · 620 lines · 25 tokens per session scan A a765722990c5
effect-filesystem is a skill published in the GitHub repository mpsuesser/pi-effect-harness (24 stars, last pushed 2mo ago), licensed MIT. It adds 25 tokens to every session and 3,678 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
Other skills, from other repositories
effect-patterns-concurrency
Effect-TS patterns for Concurrency. Use when working with concurrency in Effect-TS applications.
effect-patterns-making-http-requests
Effect-TS patterns for Making Http Requests. Use when working with making http requests in Effect-TS applications.
effect-patterns-streams
Effect-TS patterns for Streams. Use when working with streams in Effect-TS applications.
effect-patterns-error-handling
Effect-TS patterns for Error Handling. Use when working with error handling in Effect-TS applications.
effect-patterns-streams-sinks
Effect-TS patterns for Streams Sinks. Use when working with streams sinks in Effect-TS applications.
effect-patterns-resource-management
Effect-TS patterns for Resource Management. Use when working with resource management in Effect-TS applications.