pikku-rpc

name	pikku-rpc
description	Use when making internal function-to-function calls within a Pikku app, composing functions, or exposing RPC endpoints. Covers rpc.invoke, rpc.remote, rpc.exposed, and generated RPC client. TRIGGER when: code uses wire.rpc or expose: true, user asks about calling one Pikku function from another, function composition, or RPC endpoints. DO NOT TRIGGER when: user asks about HTTP routes (use pikku-http) or addon cross-package calls (use pikku-addon).
installGroups	["core"]

Pikku RPC Wiring

Agent Operating Procedure

Use this skill as an execution checklist, not reference material.

1. Discover before editing. Prefer OpenCode tools such as pikku-meta when available; otherwise run the relevant pikku meta ... --json command and inspect only the focused output you need.
2. Identify the source files that own the behavior. Do not start by reading generated output, .pikku, node_modules, vendored packages, or broad build artifacts.
3. Make the smallest source change that satisfies the task. Keep generated files generated, and avoid hand-editing SDKs, schema output, or typegen.
4. Validate with the narrowest relevant command first, then run pikku-verify or pikku all when functions, wirings, schemas, or generated clients may have changed.
5. If validation fails, fix the source cause and rerun validation. Do not paper over generated errors by editing generated files.

Call Pikku functions from other Pikku functions internally with full type safety. Use RPC to compose business logic without importing functions directly.

Before You Start

pikku info functions --verbose   # See existing functions and which could be called via RPC
pikku info tags --verbose        # Understand project organization

See pikku-concepts for the core mental model.

API Reference

RPC Methods (on wire.rpc)

Four ways to call functions via RPC:

Method	Purpose
rpc.invoke(name, data)	Internal call to any wired function
rpc.remote(name, data)	Remote call via DeploymentService
rpc.exposed(name, data)	Call functions marked with expose: true
rpc.startWorkflow(name, input)	Start a workflow

Exposed Functions

Mark a function as externally callable via RPC:

const greet = pikkuSessionlessFunc({
  title: 'Greet',
  expose: true, // ← callable via rpc.exposed()
  func: async ({}, { name }) => {
    return { message: `Hello, ${name}!` }
  },
})

HTTP RPC Endpoint

Expose all expose: true functions over HTTP:

wireHTTP({
  route: '/rpc/:rpcName',
  method: 'post',
  auth: false,
  func: rpcCaller,
})

Usage Patterns

Internal Function Composition

const calculateTax = pikkuSessionlessFunc({
  title: 'Calculate Tax',
  func: async ({}, { amount, rate }) => {
    return { tax: amount * rate }
  },
})

const processOrder = pikkuFunc({
  title: 'Process Order',
  func: async ({ db }, { orderId }, { rpc }) => {
    const order = await db.getOrder(orderId)

    // Call another pikku function internally — fully typed
    const { tax } = await rpc.invoke('calculateTax', {
      amount: order.total,
      rate: 0.08,
    })

    return { orderId, total: order.total + tax }
  },
})

When to Use RPC vs Direct Imports

Approach	Use When
rpc.invoke()	Cross-domain calls, maintaining separation of concerns, function may be in different package
Direct import	Same module, tightly coupled logic, performance critical

RPC calls go through Pikku's middleware and permission pipeline. Direct imports skip them.

Generated RPC Client

After npx pikku all:

import { pikkuRPC } from '.pikku/pikku-rpc.gen.js'

pikkuRPC.setServerUrl('http://localhost:4002')

const result = await pikkuRPC.invoke('calculateTax', {
  amount: 100,
  rate: 0.08,
})

pikkuRPC.setAuthorizationJWT(token)

Complete Example

// functions/billing.functions.ts
export const calculateTax = pikkuSessionlessFunc({
  title: 'Calculate Tax',
  func: async ({}, { amount, region }) => {
    const rates = { US: 0.08, EU: 0.2, UK: 0.2 }
    return { tax: amount * (rates[region] || 0) }
  },
})

export const calculateShipping = pikkuSessionlessFunc({
  title: 'Calculate Shipping',
  func: async ({}, { weight, region }) => {
    const base = region === 'US' ? 5 : 15
    return { shipping: base + weight * 0.5 }
  },
})

// functions/orders.functions.ts
export const processOrder = pikkuFunc({
  title: 'Process Order',
  func: async ({ db }, { orderId }, { rpc }) => {
    const order = await db.getOrder(orderId)

    const { tax } = await rpc.invoke('calculateTax', {
      amount: order.total,
      region: order.region,
    })

    const { shipping } = await rpc.invoke('calculateShipping', {
      weight: order.totalWeight,
      region: order.region,
    })

    const finalTotal = order.total + tax + shipping
    await db.updateOrder(orderId, { tax, shipping, finalTotal })

    return { orderId, total: finalTotal, tax, shipping }
  },
})