cli-design

name	cli-design
displayName	CLI Design
description	Design and build agent-first CLIs with HATEOAS JSON responses, context-protecting output, and self-documenting command trees. Use when creating new CLI tools, adding commands to existing CLIs (joelclaw, slog), or reviewing CLI design for agent-friendliness. Triggers on 'build a CLI', 'add a command', 'CLI design', 'agent-friendly output', or any task involving command-line tool creation.
version	1.1.0
author	Joel Hooks
tags	["joelclaw","cli","agentic","ux","json"]

Agent-First CLI Design

CLIs in this system are agent-first, human-distant-second. Every command returns structured JSON that an agent can parse, act on, and follow. Humans are welcome to pipe through jq.

Core Principles

1. JSON always

Every command returns JSON. No plain text. No tables. No color codes. Agents parse JSON; they don't parse prose.

# This is the ONLY output format
joelclaw status
# → { "ok": true, "command": "joelclaw status", "result": {...}, "next_actions": [...] }

No --json flag. No --human flag. JSON is the default and only format.

2. HATEOAS — every response tells you what to do next

Every response includes next_actions — an array of command templates the agent can run next. Templates use standard POSIX/docopt placeholder syntax:

• <placeholder> — required argument
• [--flag <value>] — optional flag with value
• [--flag] — optional boolean flag
• No params field — literal command (run as-is)
• params present — template (agent fills placeholders)
• params.*.value — pre-filled from context (agent can override)
• params.*.default — value if omitted
• params.*.enum — valid choices

{
  "ok": true,
  "command": "joelclaw send pipeline/video.download",
  "result": {
    "event_id": "01KHF98SKZ7RE6HC2BH8PW2HB2",
    "status": "accepted"
  },
  "next_actions": [
    {
      "command": "joelclaw run <run-id>",
      "description": "Check run status for this event",
      "params": {
        "run-id": { "value": "01KHF98SKZ7RE6HC2BH8PW2HB2", "description": "Run ID (ULID)" }
      }
    },
    {
      "command": "joelclaw logs <source> [--lines <lines>] [--grep <text>] [--follow]",
      "description": "View worker logs",
      "params": {
        "source": { "enum": ["worker", "errors", "server"], "default": "worker" }
      }
    },
    {
      "command": "joelclaw status",
      "description": "Check system health"
    }
  ]
}

next_actions are contextual — they change based on what just happened. A failed command suggests different next steps than a successful one. Templates are the agent's affordances — they show what's parameterizable, what values are valid, and what the current context pre-fills.

3. Self-documenting command tree

Agents discover commands via two paths: the root command (JSON tree) and --help (Effect CLI auto-generated). Both must be useful.

Root command (no args) returns the full command tree as JSON:

{
  "ok": true,
  "command": "joelclaw",
  "result": {
    "description": "JoelClaw — personal AI system CLI",
    "health": { "server": {...}, "worker": {...} },
    "commands": [
      { "name": "send", "description": "Send event to Inngest", "usage": "joelclaw send <event> -d '<json>'" },
      { "name": "status", "description": "System status", "usage": "joelclaw status" },
      { "name": "gateway", "description": "Gateway operations", "usage": "joelclaw gateway status" }
    ]
  },
  "next_actions": [...]
}

--help output is auto-generated by Effect CLI from Command.withDescription(). Every subcommand must have a description — agents always call --help and a bare command list with no descriptions is useless.

// ❌ Agents see a blank command list
const status = Command.make("status", {}, () => ...)

// ✅ Agents see what each command does
const status = Command.make("status", {}, () => ...).pipe(
  Command.withDescription("Active sessions, queue depths, Redis health")
)

COMMANDS
  - status                          Active sessions, queue depths, Redis health
  - diagnose [--hours integer]      Layer-by-layer health check
  - review [--hours integer]        Recent session context

4. Context-protecting output

Agents have finite context windows. CLI output must not blow them up.

Rules:

• Terse by default — minimum viable output
• Auto-truncate large outputs (logs, lists) at a reasonable limit
• When truncated, include a file path to the full output
• Never dump raw logs, full transcripts, or unbounded lists

{
  "ok": true,
  "command": "joelclaw logs",
  "result": {
    "lines": 20,
    "total": 4582,
    "truncated": true,
    "full_output": "/var/folders/.../joelclaw-logs-abc123.log",
    "entries": ["...last 20 lines..."]
  },
  "next_actions": [
    {
      "command": "joelclaw logs <source> [--lines <lines>]",
      "description": "Show more log lines",
      "params": {
        "source": { "enum": ["worker", "errors", "server"], "default": "worker" },
        "lines": { "default": 20, "description": "Number of lines" }
      }
    }
  ]
}

5. Errors suggest fixes

When something fails, the response includes a fix field — plain language telling the agent what to do about it.

{
  "ok": false,
  "command": "joelclaw send pipeline/video.download",
  "error": {
    "message": "Inngest server not responding",
    "code": "SERVER_UNREACHABLE"
  },
  "fix": "Start the Inngest server pod: kubectl rollout restart statefulset/inngest -n joelclaw",
  "next_actions": [
    { "command": "joelclaw status", "description": "Re-check system health after fix" },
    {
      "command": "kubectl get pods [--namespace <ns>]",
      "description": "Check pod status",
      "params": { "ns": { "default": "joelclaw" } }
    }
  ]
}

Response Envelope

Every command uses this exact shape:

Success

{
  ok: true,
  command: string,          // the command that was run
  result: object,           // command-specific payload
  next_actions: Array<{
    command: string,        // command template (POSIX syntax) or literal
    description: string,    // what it does
    params?: Record<string, {   // presence = command is a template
      description?: string,     // what this param means
      value?: string | number,  // pre-filled from current context
      default?: string | number,// value if omitted
      enum?: string[],          // valid choices
      required?: boolean        // true for <positional> args
    }>
  }>
}

Error

{
  ok: false,
  command: string,
  error: {
    message: string,        // what went wrong
    code: string            // machine-readable error code
  },
  fix: string,              // plain-language suggested fix
  next_actions: Array<{
    command: string,        // command template or literal
    description: string,
    params?: Record<string, { ... }>  // same schema as success
  }>
}

Reference implementations

• joelclaw — ~/Code/joelhooks/joelclaw/packages/cli/ (Effect CLI, operational surface)
• slog — system log CLI (same envelope patterns)

Use these as the current envelope source-of-truth.

Implementation

Framework: Effect CLI (@effect/cli)

All CLIs use @effect/cli with Bun. This is non-negotiable — consistency across the system matters more than framework preference.

import { Command, Options } from "@effect/cli"
import { NodeContext, NodeRuntime } from "@effect/platform-node"

const send = Command.make("send", {
  event: Options.text("event"),
  data: Options.optional(Options.text("data").pipe(Options.withAlias("d"))),
}, ({ event, data }) => {
  // ... execute, return JSON envelope
})

const root = Command.make("joelclaw", {}, () => {
  // Root: return health + command tree
}).pipe(Command.withSubcommands([send, status, logs]))

Binary distribution

Build with Bun, install to ~/.bun/bin/:

bun build src/cli.ts --compile --outfile joelclaw
cp joelclaw ~/.bun/bin/

Adding a new command

1. Define the command with Command.make
2. Return the standard JSON envelope (ok, command, result, next_actions)
3. Include contextual next_actions — what makes sense AFTER this specific command
4. Handle errors with the error envelope (ok: false, error, fix, next_actions)
5. Add to the root command's subcommands
6. Add to the root command's commands array in the self-documenting output
7. Rebuild and install

Streaming Protocol (NDJSON) — ADR-0058

Request-response covers the spatial dimension (what's the state now?). Streamed NDJSON covers the temporal dimension (what's happening over time?). Together they make the full system observable through one protocol.

When to stream

Stream when the command involves temporal operations — watching, following, tailing. Not every command needs streaming. Point-in-time queries (status, functions, runs) stay as single envelopes.

Streaming is activated by command semantics (--follow, watch, gateway stream), never by a global --stream flag.

Protocol: typed NDJSON with HATEOAS terminal

Each line is a self-contained JSON object with a type discriminator. The last line is always the standard HATEOAS envelope (result or error). Tools that don't understand streaming read the last line and get exactly what they expect.

{"type":"start","command":"joelclaw send video/download --follow","ts":"2026-02-19T08:25:00Z"}
{"type":"step","name":"download","status":"started","ts":"..."}
{"type":"progress","name":"download","percent":45,"ts":"..."}
{"type":"step","name":"download","status":"completed","duration_ms":3200,"ts":"..."}
{"type":"step","name":"transcribe","status":"started","ts":"..."}
{"type":"log","level":"warn","message":"Large file, chunked transcription","ts":"..."}
{"type":"step","name":"transcribe","status":"completed","duration_ms":45000,"ts":"..."}
{"type":"result","ok":true,"command":"...","result":{...},"next_actions":[...]}

Stream event types

Type	Meaning	Terminal?
start	Stream begun, echoes command	No
step	Inngest step lifecycle (started/completed/failed)	No
progress	Progress update (percent, bytes, message)	No
log	Diagnostic message (info/warn/error level)	No
event	An Inngest event was emitted (fan-out visibility)	No
result	HATEOAS success envelope — always last	Yes
error	HATEOAS error envelope — always last	Yes

TypeScript types

import type { NextAction } from "./response"

type StreamEvent =
  | { type: "start"; command: string; ts: string }
  | { type: "step"; name: string; status: "started" | "completed" | "failed"; duration_ms?: number; error?: string; ts: string }
  | { type: "progress"; name: string; percent?: number; message?: string; ts: string }
  | { type: "log"; level: "info" | "warn" | "error"; message: string; ts: string }
  | { type: "event"; name: string; data: unknown; ts: string }
  | { type: "result"; ok: true; command: string; result: unknown; next_actions: NextAction[] }
  | { type: "error"; ok: false; command: string; error: { message: string; code: string }; fix: string; next_actions: NextAction[] }

Emitting stream events

Use the emit() helper — one JSON line per call, flushed immediately:

import { emit, emitResult, emitError } from "../stream"

// Progress events
emit({ type: "start", command: "joelclaw send video/download --follow", ts: new Date().toISOString() })
emit({ type: "step", name: "download", status: "started", ts: new Date().toISOString() })
emit({ type: "step", name: "download", status: "completed", duration_ms: 3200, ts: new Date().toISOString() })

// Terminal — always last
emitResult("send --follow", { videoId: "abc123" }, [
  { command: "joelclaw run abc123", description: "Inspect the completed run" },
])

Redis subscription pattern

Streaming commands subscribe to the same Redis pub/sub channels the gateway extension uses. pushGatewayEvent() middleware is the emission point — the CLI is just another subscriber.

import { streamFromRedis } from "../stream"

// Subscribe to a channel, transform events, emit NDJSON
await streamFromRedis({
  channel: `joelclaw:notify:gateway`,
  command: "joelclaw gateway stream",
  transform: (event) => ({
    type: "event" as const,
    name: event.type,
    data: event.data,
    ts: new Date().toISOString(),
  }),
  // Optional: end condition
  until: (event) => event.type === "loop.complete",
})

Composable with Unix tools

NDJSON is pipe-native. Agents and humans can filter streams:

# Only step events
joelclaw watch | jq --unbuffered 'select(.type == "step")'

# Only failures
joelclaw send video/download --follow | jq --unbuffered 'select(.type == "error" or (.type == "step" and .status == "failed"))'

# Count steps
joelclaw send pipeline/run --follow | jq --unbuffered 'select(.type == "step" and .status == "completed")' | wc -l

Agent consumption pattern

Agents consuming streams read lines as they arrive and can make decisions mid-execution:

1. Start the stream: joelclaw send video/download --follow
2. Read lines incrementally
3. React to early signals (cancel if error, escalate if slow, log progress)
4. The terminal result/error line contains next_actions for what to do after

This eliminates the polling tax — no wasted tool calls checking "is it done yet?"

Cleanup

Streaming commands hold a Redis connection. They must:

• Handle SIGINT/SIGTERM gracefully (disconnect Redis, emit terminal event)
• Use connectTimeout and commandTimeout to prevent hangs
• Clean up the subscription on stream end (success, error, or signal)

Anti-Patterns

Don't	Do
Plain text output	JSON envelope
Tables with ANSI colors	JSON arrays
--json flag to opt into JSON	JSON is the only format
Dump 10,000 lines	Truncate + file pointer
Error: something went wrong	{ ok: false, error: {...}, fix: "..." }
Undiscoverable commands	Root returns full command tree
Static help text	HATEOAS next_actions
console.log("Success!")	{ ok: true, result: {...} }
Exit code as the only error signal	Error in JSON + exit code
Require the agent to read --help	Root command self-documents
Subcommand with no withDescription	Every command gets a description for --help
Poll in a loop for temporal data	Stream NDJSON via Redis sub (ADR-0058)
Plain text in streaming commands	Every line is a typed JSON object
Hold Redis connections without cleanup	SIGINT handler + connection timeout

Naming Conventions

• Commands are nouns or verbs, lowercase, no hyphens: send, status, logs, gateway
• Subcommands follow naturally: joelclaw search "query", joelclaw loop start
• Flags use --kebab-case: --max-quality, --follow
• Short flags for common options: -d for --data, -f for --follow
• Event names use domain/action: pipeline/video.download, content/summarize

Checklist for New Commands

• Returns JSON envelope (ok, command, result, next_actions)
• Command.withDescription() set (shows in --help)
• Error responses include fix field
• Root command lists this command in its tree
• Output is context-safe (truncated if potentially large)
• next_actions are contextual to what just happened
• next_actions with variable parts use template syntax (<required>, [--flag <value>]) + params
• Context-specific values pre-filled via params.*.value
• No plain text output anywhere
• No ANSI colors or formatting
• Works when piped (no TTY detection)
• Builds and installs to ~/.bun/bin/