Skill, Agent, or Module? What Should I Build?

Use this guide to decide what type of BMad component to build based on your needs.

Prerequisites

• Familiarity with what skills, agents, workflows, and modules are
• A problem you want to solve or an idea you want to explore
• 5-10 minutes to work through the decision tree

When to Use This Guide

Use this when you’re:

• Starting a new BMad project and unsure what to build
• Deciding if your idea needs an agent or could be a simpler skill
• Planning whether to invest in a full module with multiple agents and workflows

Quick Decision Tree

flowchart TD
    A[What do you want to build?] --> B{Does it have a<br/>helpful persona?}
    B -->|No| C{Is it a single<br/>focused task?}
    B -->|Yes| D{Does it need to<br/>remember things<br/>between sessions?}
    C -->|Yes| E[Skill<br/>one-shot utility]
    C -->|No| F{Does it guide<br/>through a process?}
    D -->|No| G[Agent<br/>persona with menu actions]
    D -->|Yes| H[Agent<br/>with memory/sidecar]
    F -->|Yes| I[Workflow<br/>step-by-step process]
    F -->|No| J{Multiple related<br/>personas and processes?}
    J -->|Yes| K[Module<br/>agents + workflows]
    J -->|No| G

    style E fill:#c8e6c9
    style G fill:#fff9c4
    style H fill:#ffe082
    style I fill:#e1f5fe
    style K fill:#f3e5f5

Understanding the Hierarchy

BMad components build on each other:

Skill (action) → Agent (persona with skills) → Module (agents + workflows)

Component	What It Is	Key Feature
Skill	A single action	No persona — just does something
Agent	A helpful persona	Menu-driven skills, optional memory
Workflow	A guided process	Steps with facilitation, may have persona
Module	Integrated system	Multiple agents + workflows, shared purpose

Agent = Helpful Persona

Think of agents as helpful personas with skills in their menu. An agent may or may not have memory (sidecar) depending on whether it needs to remember things between sessions.

The Key Difference: Does It Need a Persona?

The first question to ask: Does your idea need a helpful persona?

Has a Persona?	Build This…	Why
Yes	Agent (with or without memory)	Agents ARE personas — helpful characters with skills in their menu
No	Skill or Workflow	Skills and workflows DO things. They don’t need to be someone

Persona Check

If you can describe your creation as “he” or “she” — if it has a name, a voice, a way of interacting — it’s an agent. If it’s just “it” — a thing that performs a function — it’s probably a skill.

Type Comparison

Skill

Best for: Single-purpose utilities that don’t need a persona.

Characteristics
Persona	None — it’s a tool, not a character
Memory	None — each use is independent
Complexity	Low — one thing, done well
Building time	5-10 minutes
Example ideas	Currency converter, tip calculator, unit converter, timestamp formatter, QR code generator

When to choose:

• Task is straightforward and single-purpose
• No conversation needed — input → output
• No persona required — it’s a utility
• You want the fastest path to a working tool

When NOT to choose:

• You want a friendly, funny, or themed experience
• The task benefits from conversation or clarification
• You want to build a relationship with users

Build with: Add to any existing agent or workflow as a skill/action

Agent

Best for: A helpful persona with related skills available through a menu.

Characteristics
Persona	Yes — has a name, voice, character
Skills	Baked into menu — user selects from available actions
Memory	Optional — add sidecar if it needs to remember things
Complexity	Low-Medium — focused persona with related skills
Building time	15-60 minutes

Memory? Add a sidecar if your agent needs to remember:

• User preferences or settings
• Project state or history
• Past decisions or progress
• Long-term tracking

No memory needed when:

• Each conversation is independent
• Skills are simple (1-2 prompt lines each)
• Nothing to carry forward between sessions

Example ideas:

Without Memory	With Memory
Commit Poet (poetic commit messages)	Novel writing companion
Snarky Weather Bot	Fitness coach with PR tracking
Pun-making Barista	Therapist agent
Motivational Gym Bro	Language tutor
Sassy Fortune Teller	Financial planner

When to choose:

• You want a specific persona or voice
• All skills are related to that persona’s purpose
• Interaction happens through menu selection
• Skills are simple enough to be 1-2 prompt lines each

Build with: bmad:bmb:agents:agent-builder — add sidecar if memory is needed

Workflow

Best for: Guided processes where users move through defined steps.

Characteristics
Persona	Optional — can have a guide or be neutral facilitator
Memory	Optional — can be stateless or track progress
Complexity	Medium — multiple steps with decision points
Building time	30-45 minutes
Example ideas	Brainstorming session, trip planning process, workout builder, tax preparation flow, meditation session, journaling practice

When to choose:

• Process has clear stages or steps
• Users benefit from guidance and progressive disclosure
• Process benefits from structure
• May or may not have a guide persona

Build with: bmad:bmb:workflows:workflow-builder

Module

Best for: Complete solutions with multiple agents and workflows working together.

Characteristics
Components	Multiple agents + multiple workflows
Key distinction	Workflows are primary — agents are personas that workflows reference
Sequence	Often has implied journey or phases
Complexity	High — coordinated system
Building time	2-4 hours (including component building)
Example ideas	Wedding planner, legal office suite, mental wellness program, fitness coaching system, D&D campaign toolkit, kitchen companion

Agents in Modules

In a module, agents serve as persona references. The workflows themselves contain the actual persona — each workflow speaks in the voice of the relevant agent. The module’s agents define who these personas are, but the workflows bring them to life. Agents in modules may or may not have sidecars depending on whether they need memory.

When to choose:

• Multiple related capabilities work better together
• Different personas for different aspects
• Guided journeys through processes
• Want to share or publish a complete solution
• Users benefit from integrated experience

Build with: Morgan ([PB] → [CM])

Decision Questions

Question 1: Does It Have a Persona?

Persona means: A helpful character with a name, voice, and way of interacting.

If Your Idea Has…	Build This…
A character, voice, or style	Agent
Just does a task, no character	Skill or Workflow

Examples:

Idea	Persona?	Type
”Convert currencies”	No — just a calculation	Skill
”A snarky weather bot that complains about your location”	Yes — sarcastic character	Agent
”A motivational gym bro who hypes you up”	Yes — enthusiastic bro persona	Agent
”Generate QR codes”	No — just a utility	Skill
”A sassy fortune teller”	Yes — mystical, dramatic character	Agent
”Calculate tips”	No — just math	Skill

Question 2: Does It Need Memory?

Memory means: Remembering information between conversations — user preferences, project state, past decisions, progress tracking.

If You Need Memory…	Build This…
User preferences, settings, ongoing projects	Agent with sidecar
Long-term tracking, progress over time	Agent with sidecar
Each conversation is independent	Agent (no sidecar) or Skill

Examples:

Idea	Memory Needed?	Type
”Motivational gym bro”	No — hypes you up fresh each time	Agent (no sidecar)
“Fitness coach who remembers your PRs and tracks progress”	Yes — needs your workout history	Agent with sidecar
”Snarky weather bot”	No — each weather check is independent	Agent (no sidecar)
“Writing companion who remembers your novel’s characters”	Yes — needs story context	Agent with sidecar
”Sassy fortune teller”	No — each reading is standalone	Agent (no sidecar)
“Language tutor who tracks your vocabulary”	Yes — needs your learning history	Agent with sidecar

Question 3: Single Task or Guided Process?

If Your Idea Is…	Build This…
One-shot utility (no persona)	Skill
One-shot utility (WITH persona)	Agent
Guided multi-step process	Workflow
Multiple personas + processes	Module

Examples:

Idea	Type	Why
”Currency converter”	Skill	Utility, no persona, no steps
”Pun-making barista”	Agent	One persona, related skills in menu
”Plan a trip”	Workflow	Guided multi-step process
”Complete kitchen suite: recipes + meals + groceries”	Module	Multiple personas (chef, planner) + processes

Question 4: Should It Be a Module?

The key distinction: Does it need multiple agents and workflows working together?

Module Indicators	Build Module When…
Multiple personas	Different aspects need different voices
Workflow-driven	Processes have steps with facilitation
Related capabilities	Things work better together
Implied journey	Phases or sequence make sense

Remember: In a module, workflows are primary. Agents define the personas, but workflows contain the actual persona in their steps.

Real-World Decision Examples

Example 1: “I want a currency converter”

Questions:

• Persona? No — just converts numbers
• Memory needed? No — each conversion is independent
• Single task? Yes

Decision: Skill

• Add as an action to any agent
• Input: amount and currencies
• Output: converted amount
• No conversation needed

Example 2: “I want a commit message poet”

Questions:

• Persona? Yes — poetic drama, “Inkwell Von Comitzen”
• Memory needed? No — each commit is independent
• Skills related? Yes — all about commit messages in different styles (haiku, conventional, story, etc.)
• Each skill is 1-2 prompt lines

Decision: Agent (no sidecar) — “Commit Poet”

• Persona: Poetic drama and flair
• Skills (menu items): Write commit, analyze changes, improve message, batch commits, conventional format, story format, haiku format
• All skills fit the persona
• No workflow needed — menu-driven
• No memory needed

Example 3: “I want a snarky weather bot”

Questions:

• Persona? Yes — sarcastic, complains about your location
• Memory needed? No — each weather check is independent
• Single skill? Essentially yes — fetch weather and add snark

Decision: Agent (no sidecar)

• Character: “Storm” the grumpy meteorologist
• Voice: Sarcastic, complains about humidity, judges your location choices
• No memory — fresh snark each time

Example 4: “I want help planning my wedding”

Questions:

• Multiple personas? Yes — budget specialist (analytical), vendor coordinator (organized), timeline manager (detail-oriented)
• Workflow-driven? Yes — budget workshop, vendor vetting, day-of schedule
• Related capabilities? Yes — all part of wedding planning
• Implied journey? Yes — budget → vendors → timeline

Decision: Module — “Wedding Planner”

• Agents define personas: Budget Specialist, Vendor Coordinator, Timeline Manager
• Workflows carry the personas: Each workflow speaks in the relevant agent’s voice
• Workflows guide users through processes step-by-step
• Agents are referenced by workflows, not used directly

Example 5: “I want a fitness buddy”

Questions:

• Persona? Yes — motivational, tough-love, or gentle cheer
• Memory needed? Yes — needs to remember your workouts, PRs, goals
• Single persona or multiple? One persona fits

Decision: Agent with sidecar — “Fitness Buddy”

• Persona: Motivational gym bro (or gentle encourager)
• Remembers: Your PRs, workout history, preferences, goals
• Tracks progress over time
• Menu-driven skills: Log workout, view progress, suggest exercises, etc.

Example 6: “I want a wellness program”

Questions:

• Multiple personas? Yes — wellness companion (empathetic), meditation guide (serene)
• Workflow-driven? Yes — daily checkin, wellness journal, guided meditation
• Related capabilities? Yes — all part of mental wellness
• Implied journey? Yes — checkin → journal → meditate

Decision: Module — “Wellness Companion”

• Agents: Wellness Companion (Riley), Meditation Guide (Serenity)
• Workflows: Daily Checkin (Riley’s voice), Wellness Journal (Riley’s voice), Guided Meditation (Serenity’s voice)
• Workflows contain the actual persona in their steps
• anytime skills: Quick breathing, mood check (agent menu items)

Example 7: “I want a tip calculator”

Questions:

• Persona? No — just math
• Memory needed? No — each bill is independent
• Single task? Yes

Decision: Skill

• Simple utility
• Add to any agent as an action
• Input: bill amount, tip percentage, party size
• Output: per-person amount

Make It Fun?

You COULD make “Tip Calculator” an Agent with personality (like a sassy waiter who judges your tipping). But ask: is the persona adding value? If it’s just a one-time calculation, a skill is faster and simpler.

Starting Small, Growing Big

You don’t have to start with a module. Many successful modules grow from simpler beginnings:

Start As	Evolve Into	Example
Skill	Agent	Unit converter → Snarky converter with persona
Agent (no memory)	Agent with sidecar	Motivational quotes → Fitness coach with memory
Agent	Module	Novel helper → Story Architect Module with multiple agents and workflows
Workflow	Module	Brainstorming → Creative Intelligence Suite

Iterate

Build the smallest thing that solves your core problem. Add complexity only when needed. Your users will tell you what’s missing.

What You Get

After working through this guide, you’ll know:

• Whether to build a skill, agent, or module
• Whether your agent needs memory (sidecar)
• Whether your idea justifies a full module with multiple agents and workflows
• The appropriate builder workflow to use

Next Steps

Once you’ve decided:

If You Chose…	Next Step
Skill	Add as an action to an existing agent or workflow
Agent	Create a Custom Agent
Agent with sidecar	Create a Custom Agent (enable sidecar)
Workflow	Create Your First Workflow
Module	Create Your First Module
Still Unsure	Discover Your Module Idea

Tips

Start with the problem, not the solution. “I need a module” is starting with solution. “I need to plan meals for my family” is starting with problem.

Build for yourself first. If you genuinely need and use it, others will too.

Keep scope tight. Your first creation should do ONE thing well. Add features later.

Personas are optional. Not everything needs a character. Utilities are valuable too.

Think ecosystem. Your “Meal Planner Agent” could complement someone else’s “Recipe Generator Module.” Collaboration beats competition.

No Wrong Choice

Whatever you choose, you’re learning. Skills can grow into agents. Agents can evolve into modules. Build something, use it, and let it evolve.