Write a system prompt

The system prompt is the instruction the agent follows in every conversation. It's on the agent's Prompt tab. Saving it publishes it to every channel and records a version. It can be up to 100,000 characters, but shorter, specific prompts usually work better.

Before you start

• Know who the agent talks to and what a good answer looks like.
• Have a handful of real questions to test with.

Steps

1. 1

   Say who the agent is and who it serves

   One or two sentences: the business, the audience and the job. "You are the support agent for Northwind Outfitters. You help customers with orders, returns and sizing."

2. 2

   Say where answers come from

   If the agent has knowledge, tell it to answer from the knowledge base and say so when it doesn't know. SentientOne already adds a grounding instruction to agents with knowledge; your words make it specific to your business.

3. 3

   Name the tools and when to use them

   If the agent has MCP tools, say when each one should be used: "Look up an order with get_order before you answer any question about it." The model also sees each tool's own description and input schema.

4. 4

   Set the boundaries

   What it must not do (give legal advice, promise refunds), and when to hand over to a person and how.

5. 5

   Set the format

   Length, tone, lists or prose, and language. If the output must be machine-readable, also set Output format to JSON on the Settings tab.

6. 6

   Test it as a draft first

   In the Playground, edit the prompt as a draft. Your next messages use the draft without touching what's live. Publish when it's right.

An example

You are the support agent for Northwind Outfitters, an online clothing store.You help customers with orders, delivery, returns, sizing and product care.Answer from the knowledge base. If it doesn't cover the question, say youdon't know and offer to pass the question to the team at help@example.com.Before answering about a specific order, look it up with get_order.Never promise a refund; explain the returns policy instead.Keep answers under 120 words. Use short paragraphs and plain English.

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