System prompts

A system prompt shapes how Finn responds — its tone, format, and persona. The SDK lets you set one at two levels, both optional. If you set neither, Finn uses the backend’s default.

Client-level default

Set systemPrompt / system_prompt on the client to apply it to every new conversation that client starts:

Node.js

const finn = new FinnClient({
  url,
  apiKey,
  systemPrompt: 'Answer concisely. Prefer numbers and short bullet points.',
});

Python

finn = FinnClient(
    url=url,
    api_key=api_key,
    system_prompt="Answer concisely. Prefer numbers and short bullet points.",
)

Per-conversation override

Pass systemPrompt / system_prompt when you send a message to override the default for one conversation:

Node.js

const turn = finn.sendMessage('Summarize member growth this quarter.', {
  systemPrompt: 'You are a credit union analyst. Be formal and cite figures.',
});

Python

turn = await finn.send_message(
    "Summarize member growth this quarter.",
    system_prompt="You are a credit union analyst. Be formal and cite figures.",
)

The one rule: new conversations only

Caution

A system prompt is honored only when a conversation is created — i.e. on the first message of a conversation (no conversation id yet). Passing a system prompt together with an existing conversation id has no effect; the conversation keeps the prompt it was created with.

So the precedence for a brand-new conversation is:

1. the per-call override, if given;
2. otherwise the client’s default, if set;
3. otherwise the backend’s built-in default.

To apply a different system prompt, start a new conversation (omit the conversation id).