discord-manager: Skill for Claude Code

Composable Functions

Everything here documents the repository as it is on main. If main disagrees with this file, main wins: follow it and flag the drift.

Every function in app/business/ is a composable built with composable-functions (v5). This is what makes the layer callable identically from an MCP tool, a gateway handler, a scheduled job, a seed, and a test.

Core types

Composable

A function that returns Promise<Result<T>>:

import { composable } from 'composable-functions'

const add = composable((a: number, b: number) => a + b)
//    ^? Composable<(a: number, b: number) => number>

Result

A union of success and failure:

type Result<T> = Success<T> | Failure

// Success
{ success: true, data: T, errors: [] }

// Failure
{ success: false, errors: Error[] }

Always check success before reading data:

const result = await fn()
if (!result.success) {
  return
}
// result.data is type-safe here

Error types

InputError

Validation errors about caller input. Every InputError carries the path of the field it is about, so the caller can tell which argument to fix:

import { InputError } from 'composable-functions'

throw new InputError('That message is not in an ingested channel', ['messageLink'])

A pathless InputError leaves the caller guessing — always name the field. The one shape that legitimately goes pathless is a contradiction between two fields, where naming either one alone would mislead: a schema-level refinement refusing channelId and messageId together may carry no path, provided its message names both fields and says how to choose — the way oneAnchorMessage in app/business/threads.common.ts does. Never pin such an error to one of the two fields arbitrarily just to satisfy this rule.

ContextError

Authorization and configuration errors:

import { ContextError } from 'composable-functions'

throw new ContextError('This deployment cannot send messages', ['canSendMessages'])