Skip to Content
SynapseX ChatCustom skills

Create reusable custom skills

A custom skill is a named block of instructions that is applied automatically in every conversation, without you pasting anything. By the end of this page you will have created one, verified it took effect in a fresh chat, and know how to turn it off again.

Where do I create one?

Open Work > Skills in the sidebar. The form at the top takes three things:

  1. Skill name — short and descriptive, for example Answer format
  2. Short description — what it is for, so future-you knows
  3. Instructions — the text that is applied when the skill is enabled

Click Create skill, then enable it with its toggle.

What does enabling a skill actually do?

Every skill you have enabled is concatenated into the system prompt on every turn, in every conversation — not just new ones. The assistant sees your skills under a line telling it to follow their instructions when relevant.

That has two consequences worth planning around:

  • A skill applies everywhere, so write it to be true everywhere. “Always answer in Python” is a bad skill unless you only ever write Python.
  • Skills consume context. Keep each one short and specific; three tight skills beat one long essay.

Copy this in and watch it work

Create a skill named Answer format with these instructions:

Structure every answer as follows, with no preamble:

1. One sentence that directly answers the question.
2. A short bulleted list with the supporting detail — at most five bullets.
3. A final line beginning "Caveats:" naming anything you are unsure about,
   or "Caveats: none." if there are none.

Never open with a restatement of my question.

Enable it, then open a new chat and send this test prompt:

Should I use a UUID or an auto-increment integer for a primary key?

The answer should open with one sentence taking a position, then bullets, then a line starting Caveats:. If it opens with “Great question — it depends on…” the skill is not enabled; check the toggle on the Skills page and start a fresh chat.

How skills interact with everything else

Three things stack into the same system prompt, in this order of specificity:

  1. The persona you selected in the composer — the assistant’s role
  2. Personalization — who you are and how you want to be spoken to
  3. Enabled custom skills — the rules

They combine rather than replace each other, so a contradiction between them produces a muddled answer. If a skill says “no bullet points” and Personalization sets Headers and lists to More, pick one and fix the other. See Memory and personalization.

How do I turn a skill off?

Toggle it off on the Work > Skills page to stop it being applied, or delete it outright if you will not need it again.

Confirm the change in a new chat, not the one you were already in — long conversations are the worst place to test a system-prompt change, because the earlier turns still show the old behaviour.

What is not covered here

The Skills page also shows four built-in skill toggles. This documentation does not cover them; the instructions on this page apply to skills you author yourself.

Memory and personalizationAI agents