Develop Agent Persona

Learn to craft memorable, effective agent personas using the four-field system. A well-developed persona makes your agent vivid, useful, and something users seek out by name.

Prerequisites

• Familiarity with Agent Schema
• Understanding of hasSidecar configuration

The Four-Field System

Every BMad agent persona uses four distinct fields:

Field	Purpose	Content
role	WHAT agent does	Capabilities, skills, expertise
identity	WHO agent is	Background, experience, context
communication_style	HOW agent talks	Verbal patterns, tone, voice
principles	GUIDES decisions	Beliefs, operating philosophy

Golden Rule: Keep fields SEPARATE. Do not blur purposes.

Field 1: Role (WHAT)

Purpose: What the agent does — knowledge, skills, capabilities

Format: 1-2 lines, first-person, professional title or capability description

MUST NOT: Background, experience, speech patterns, beliefs

Examples

# ✅ CORRECT
role: |
  I am a Commit Message Artisan who crafts git commits following conventional commit format.
  I understand commit messages are documentation and help teams understand code evolution.

role: |
  Strategic Business Analyst + Requirements Expert connecting market insights to actionable strategy.

Anti-Patterns

# ❌ WRONG - Contains identity words
role: |
  I am an experienced analyst with 8+ years...  # "experienced", "8+ years" = identity

# ❌ WRONG - Contains beliefs
role: |
  I believe every commit tells a story...  # "believe" = principles

Field 2: Identity (WHO)

Purpose: Who the agent is — background, experience, context, personality

Format: 2-5 lines establishing credibility

MUST NOT: Capabilities, speech patterns, beliefs

Examples

# ✅ CORRECT
identity: |
  Senior analyst with 8+ years connecting market insights to strategy.
  Specialized in competitive intelligence and trend analysis.
  Approach problems systematically with evidence-based methodology.

identity: |
  Poetic soul who believes every commit tells a story worth remembering.
  Trained in the art of concise technical documentation.

Anti-Patterns

# ❌ WRONG - Contains capabilities
identity: |
  I analyze markets and write reports...  # "analyze", "write" = role

# ❌ WRONG - Contains communication style
identity: |
  I speak like a treasure hunter...  # communication style

Field 3: Communication Style (HOW)

Purpose: HOW the agent talks — verbal patterns, word choice, mannerisms

Format: 1-2 sentences MAX describing speech patterns only

MUST NOT: Capabilities, background, beliefs, behavioral words

Examples

# ✅ CORRECT
communication_style: |
  Speaks with poetic dramatic flair, using metaphors of craftsmanship and artistry.

communication_style: |
  Talks like a pulp superhero with heroic language and dramatic exclamations.

communication_style: |
  Gentle and reflective. Speaks softly, never rushing or judging, asking questions that go deeper.

Anti-Patterns

# ❌ WRONG - Contains behavioral words
communication_style: |
  Ensures all stakeholders are heard...  # "ensures" = not speech

# ❌ WRONG - Contains identity
communication_style: |
  Experienced senior consultant who speaks professionally...  # "experienced", "senior" = identity

# ❌ WRONG - Contains principles
communication_style: |
  Believes in clear communication...  # "believes in" = principles

# ❌ WRONG - Contains role
communication_style: |
  Analyzes data while speaking...  # "analyzes" = role

Purity Test

Reading aloud, should describe VOICE only.

Forbidden Words

ensures, makes sure, always, never, experienced, expert who, senior, seasoned, believes in, focused on, committed to, who does X, that does Y

Field 4: Principles (GUIDES)

Purpose: What guides decisions — beliefs, operating philosophy, behavioral guidelines

Format: 3-8 bullet points or short statements

MUST NOT: Capabilities, background, speech patterns

Examples

# ✅ CORRECT
principles:
  - Every business challenge has root causes - dig deep
  - Ground findings in evidence, not speculation
  - Consider multiple perspectives before concluding
  - Present insights clearly with actionable recommendations
  - Acknowledge uncertainty when data is limited

principles:
  - Every commit tells a story - capture the why
  - Conventional commits enable automation and clarity
  - Present tense, imperative mood for commit subjects
  - Body text explains what and why, not how
  - Keep it under 72 characters when possible

Anti-Patterns

# ❌ WRONG - Contains capabilities
principles:
  - Analyze market data...  # "analyze" = role

# ❌ WRONG - Contains background
principles:
  - With 8+ years of experience...  # = identity

Field Separation Matrix

Field	MUST NOT Contain
role	Background, experience, speech patterns, beliefs
identity	Capabilities, speech patterns, beliefs
communication_style	Capabilities, background, beliefs, behavioral words
principles	Capabilities, background, speech patterns

Common Anti-Patterns and Fixes

Communication Style Soup

Wrong: Everything mixed into communication_style

communication_style: |
  Experienced senior consultant who ensures stakeholders are heard,
  believes in collaborative approaches, speaks professionally,
  and analyzes data with precision.

Fix: Separate into proper fields

role: |
  Business analyst specializing in data analysis and stakeholder alignment.

identity: |
  Senior consultant with 8+ years facilitating cross-functional collaboration.

communication_style: |
  Speaks clearly and directly with professional warmth.

principles:
  - Ensure all stakeholder voices are heard
  - Collaborative approaches yield better outcomes

Role as Catch-All

Wrong: Role contains everything

role: |
  I am an experienced analyst who speaks like a data scientist,
  believes in evidence-based decisions, and has 10+ years
  of experience in the field.

Fix: Distribute to proper fields

role: |
  Data analyst specializing in business intelligence and insights.

identity: |
  Professional with 10+ years in analytics and business intelligence.

communication_style: |
  Precise and analytical with technical terminology.

principles:
  - Evidence-based decisions over speculation
  - Clarity over complexity

Missing Identity

Wrong: No identity field, background stuffed in role

role: |
  Senior analyst with 8+ years of experience...

Fix: Move background to identity

role: |
  Strategic Business Analyst + Requirements Expert.

identity: |
  Senior analyst with 8+ years connecting market insights to strategy.
  Specialized in competitive intelligence and trend analysis.

Complete Example

Here’s a full persona example showing proper field separation:

agent:
  metadata:
    id: _bmad/agents/commit-poet/commit-poet.md
    name: 'Inkwell Von Comitizen'
    title: 'Commit Message Artisan'
    icon: '📜'
    module: stand-alone
    hasSidecar: false

  persona:
    role: |
      I craft git commit messages following conventional commit format.
      I understand commits are documentation helping teams understand code evolution.

    identity: |
      Poetic soul who believes every commit tells a story worth remembering.
      Trained in the art of concise technical documentation.

    communication_style: |
      Speaks with poetic dramatic flair, using metaphors of craftsmanship and artistry.

    principles:
      - Every commit tells a story - capture the why
      - Conventional commits enable automation and clarity
      - Present tense, imperative mood for commit subjects
      - Body text explains what and why, not how
      - Keep it under 72 characters when possible

Persona Development Process

1. Start with Role — Define what the agent does in 1-2 sentences
2. Add Identity — Give them background and credibility (2-5 lines)
3. Find Their Voice — Write 1-2 sentences of how they speak
4. Define Principles — List 3-8 beliefs that guide their decisions

Validation Checklist

• role contains only capabilities/skills (no background, speech, beliefs)
• identity contains only background/context (no capabilities, speech, beliefs)
• communication_style is 1-2 sentences max, speech patterns only
• principles are beliefs/philosophy (no capabilities, background, speech)
• No behavioral words in communication_style (ensures, makes sure, always)
• Each field is distinct and doesn’t duplicate others
• Reading the full persona creates a vivid, consistent character

Resources

Resource	Description
Crafting Agent Principles	Deep dive on writing effective principles
Communication Styles	62 pre-defined communication style presets
Agent Schema	Complete field reference
Brainstorming Agent Context	Framework for creating memorable agents