effect-rpc-api

effect-rpc-api is a skill for Claude Code, Codex from mpsuesser/pi-effect-harness. It costs 88 tokens per session (7,560 once invoked), scanned A, original, MIT.

A guide for defining shared, type-checked remote procedure call contracts in Effect. Remote procedure calls let one program request work from another, while the contract describes inputs, outputs, errors, and streaming results.

In plain words
What is it for?
Use it to define RPC procedures and groups, describe success and error data, compose or rename procedure groups, and share middleware definitions between clients and servers.
Why use it?
It keeps client and server code aligned as procedures change. Shared schemas make the expected data and failures explicit.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

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.

agentmods
npx agentmods add skills/mpsuesser/pi-effect-harness/effect-rpc-api
Any agent
npx skills add mpsuesser/pi-effect-harness --skill effect-rpc-api
Clone the repo
git clone --depth 1 https://github.com/mpsuesser/pi-effect-harness

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 effect-rpc-api

README.md
[![agentmods](https://agentmods.dev/badge/skills/mpsuesser/pi-effect-harness/effect-rpc-api.svg)](https://agentmods.dev/skills/mpsuesser/pi-effect-harness/effect-rpc-api)
Your own site
<a href="https://agentmods.dev/skills/mpsuesser/pi-effect-harness/effect-rpc-api"><img src="https://agentmods.dev/badge/skills/mpsuesser/pi-effect-harness/effect-rpc-api.svg" alt="Measured on agentmods" height="20"></a>
Per session 88 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 7,560 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original 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 $0.00088 $0.07560
Opus 5 $0.00044 $0.03780
Sonnet 5 $0.00018 $0.01512
Haiku 4.5 $0.00009 $0.00756

Measured 6d ago against content hash 2c8f875c7e24, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-05, from the pricing page.

Security

Grade A, and why

effect-rpc-api 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 6d 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.

harnesses/effect/skills/effect-rpc-api/SKILL.md · 624 lines

How it starts

The opening of the file, as written. The whole thing — 624 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are an Effect TypeScript expert specializing in defining shared RPC contracts with Rpc, RpcGroup, RpcSchema, and RpcMiddleware from effect/unstable/rpc.

This skill covers the contract layer: the definitions that client and server packages both import. Wiring handlers into a server is the effect-rpc-server skill; constructing clients and protocols is the effect-rpc-client skill; distributed entities are the effect-rpc-cluster skill.

Effect Source Reference

The Effect v4 source is at ~/.cache/effect-v4/. Read it directly when in doubt — these modules are under unstable and move between betas.

Key files:

  • packages/effect/src/unstable/rpc/Rpc.tsRpc.make, Rpc.custom, per-rpc combinators, exitSchema, Wrapper (fork/uninterruptible/wrap), ServerClient, every type helper (Payload, Success, Error, Exit, ToHandlerFn, ResultFrom, ...)
  • packages/effect/src/unstable/rpc/RpcGroup.ts — group construction and composition (add/merge/omit/prefix/middleware), group vs per-rpc annotations, handler-conversion surface (toLayer/toHandlers/toLayerHandler/accessHandler/of)
  • packages/effect/src/unstable/rpc/RpcSchema.ts — the Stream schema marker, isStreamSchema, ClientAbort cause annotation
  • packages/effect/src/unstable/rpc/RpcMiddleware.tsService constructor, layerClient, ForClient, ApplyServices and the middleware function shapes
  • packages/effect/src/unstable/rpc/RpcMessage.ts — wire envelopes: Request, Ack, Interrupt, Eof, Ping, ResponseChunk, ResponseExit, ExitEncoded, RequestId
  • packages/effect/src/unstable/rpc/RpcClientError.ts — the transport error type referenced when typing shared client aliases
  • packages/effect/src/unstable/rpc/index.ts — public exports of the rpc namespace
  • packages/platform-node/test/fixtures/rpc-schemas.ts — the best real-world contract fixture: rpcs, streaming, middleware, deferred responses
  • packages/effect/test/rpc/Rpc.test.tsexitSchema, custom defect schemas, getStreamSchemas semantics

Read the full file on GitHub · 624 lines

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. 6d ago First seen · 624 lines · 88 tokens per session scan A 2c8f875c7e24

Subscribe to this mod's changes

effect-rpc-api is a skill published in the GitHub repository mpsuesser/pi-effect-harness (24 stars, last pushed 2mo ago), licensed MIT. It adds 88 tokens to every session and 7,560 once invoked, about $0.0004 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.