Most teams we talk to already speak MBTI. Their slack channels have #infj and #enfp. Their hiring rubrics mention "thinkers and feelers." Their product roadmap calls one agent "the ESFJ-style support assistant." Throwing this out and replacing it with a 9-type framework is a bad idea. It feels like progress to the person introducing it. It feels like overhead to everyone else. Here is the alternative.
MBTI as the outer label
Keep MBTI exactly where it is. Use it on agent cards, on team profiles, in onboarding decks, on lanyards. It is a shared vocabulary that has earned its place by being instantly social. You do not need to retire it. You need to stop asking it to do work it is not designed to do.
Enneagram as the inner blueprint
Add the Enneagram one layer down. Inside the soul.md, inside the agent spec, inside the actual coaching conversation. Most teams that adopt this pattern end up with a simple convention:
- Public-facing materials reference MBTI. Example: "This is our ENFJ-style customer success agent."
- Internal specs reference both, with the Enneagram as the operative description. Example: "Type 2w3 sp/so, ENFJ-presenting."
- Failure modes, escalation paths, and refusal rules are written in Enneagram terms. "This agent's 2-flavoured failure mode is overcommitment — counter it with a hard task limit, not a softer system prompt."
- Tone, phrasing, and formality are written in MBTI terms. "ENFJ register: warm openings, future-oriented framing, indirect critique."
Why this works in practice
The team's existing vocabulary stays. The new layer carries the predictive weight. The handover between marketing copy ("ENFJ-style") and engineering spec ("Type 2w3, integrates to 4, disintegrates to 8") becomes clean: each layer says what only it can say, and neither one is asked to do the other's job. We have shipped this with three internal teams now. The MBTI fluency they came in with stays useful. The Enneagram layer is what closed the predictability gap they came in to fix.
“Don't replace what already works. Layer underneath it. MBTI for the room. Enneagram for the engine.”