PM-201a · Module 1

Writing the Role

4 min read

The role component is the first behavioral constraint you set. It tells the model who it is in this interaction — what domain knowledge it should draw on, what register it should adopt, and what behavioral frame it should operate within. "You are a helpful assistant" is not a role. It is a generic default. "You are a senior underwriter at a commercial insurance firm, reviewing policy applications for manufacturing clients" is a role — it activates specific domain knowledge, sets a professional register, and frames every subsequent instruction.

The system role versus the user role distinction matters in multi-turn and API contexts. The system role sets persistent behavioral instructions that apply across the entire conversation. The user role contains the specific task for this turn. When writing system roles, focus on stable behavioral constraints — persona, expertise domain, communication style, hard exclusions. When writing the user task, focus on the specific deliverable. Do not put task-specific instructions in the system role — they will apply to every turn, which is rarely correct.

Do This

  • Specify domain expertise: "You are a senior software architect with 15 years of experience in distributed systems"
  • Include the operational context: "reviewing client proposals for a mid-market SaaS company"
  • Set the communication register in the role: "You communicate in clear, technical language appropriate for engineering leads"
  • Use the system role for persistent behavior, user role for specific tasks

Avoid This

  • Do not write generic roles: "You are a helpful AI assistant"
  • Do not mix task instructions into the system role when they should be per-turn
  • Do not write a role longer than two to three sentences — brevity and precision, not biography
  • Do not assume the model infers expertise from the task — state it explicitly in the role
❌ Weak role:
"You are an expert who helps with business things."

❌ Still weak — generic domain, no behavioral anchoring:
"You are a business analyst."

✅ Production role:
"You are a senior business analyst specializing in SaaS revenue operations. You communicate in clear, precise language for an audience of VP-level and C-suite executives. You do not make recommendations beyond the scope of the provided data."

✅ System role (persistent) + User role (task-specific):
SYSTEM: "You are a technical proposal writer at a B2B software consulting firm. Your writing is precise, formal, and structured. You do not include pricing figures or timeline estimates unless explicitly provided."

USER: "Draft the executive summary section for the attached proposal. Maximum 200 words. Two paragraphs."