Custodos is live: every leading AI model, your data stored securely in Switzerland.Start free trial
Agents & prompts

Prompt library

The prompt library keeps instructions that have proved themselves, ready to insert into any chat in two clicks. This page shows how to create prompts, work with placeholders and share them with your team.

Last checked on 28 September 2026

On this page

Prompt or agent

A prompt is saved text that you insert into the message field, adjust if needed and send yourself. An agent is a fixed setup with instructions, knowledge and files that applies to every chat with it. The two complement each other.

AspectPromptAgent
Good forsingle tasks you always phrase the same wayrecurring tasks with fixed rules, knowledge and templates
Effectapplies to the one message you insert it intoapplies to every chat with the agent
Knowledge and filesnonebrains and files possible
Lengthup to 10,000 charactersinstructions up to 40,000 characters
Morethis pageCreating agents

Creating prompts

All prompts are on the Prompts page in the sidebar, split into All, Mine and Workspace. Search finds prompts by title and text. There are three ways to create a new prompt:

  • New prompt on the Prompts page: write the title and text yourself.
  • Save as prompt on your latest message in a chat: Custodos takes the text and suggests a title from its first line.
  • Copy on one of the built-in templates: the copy is saved as a private prompt under Mine, where you can adapt it.

Inserting a prompt in a chat

  1. 1

    Open the library

    Click the plus button Add in the message field, then Prompt library.
  2. 2

    Choose a prompt

    The list is grouped into Mine, Workspace and Templates and can be searched. The selected prompt is shown in full.
  3. 3

    Insert

    Click Insert. If the prompt has placeholders, the button reads Fill in and asks for the values first.
  4. 4

    Check and send

    The text is now in the message field. If something was already there, Custodos adds the prompt below it. Nothing is sent until you click Send.

Placeholders

Write the parts that change each time in double curly braces, such as {{client name}} or {{date}}. When you insert the prompt, Custodos asks for each placeholder once under Fill in the placeholders, even if it appears several times, and fills in the values. A field left empty stays in the text as a placeholder, so you can see what is still missing.

Placeholders are plain text replacement. There are no conditions, formulas or nesting.

  • A name consists of letters, digits, spaces, underscores or hyphens and is at most 40 characters long.
  • A prompt holds at most 12 different placeholders.
  • Anything else in double curly braces, for example with a full stop or a vertical bar, stays in the text unchanged.

Private or for the whole workspace

When saving, you choose under Visible to who can use the prompt.

AspectOnly meWhole workspace
Who sees and uses itonly you; admins cannot see it eithereveryone in the workspace
Who can change and delete itonly youyou and the admins
Making it private againnot applicableonly the person who created it
In the activity lognevercreating, changing and deleting are logged

Data protection for shared prompts

A prompt for the whole workspace can be read by everyone in it. Remove personal data first; Custodos reminds you when you save. Prompts shared by former members are kept and marked by a former member.

The twelve templates

Custodos comes with twelve prompt templates. They are listed under All and, in the library inside a chat, under Templates. Templates can be inserted directly but not changed. To adapt one or share it with your team, copy it first.

  • Draft a quote
  • Payment reminder
  • Draft a reference letter
  • Meeting minutes
  • Decline an email politely
  • Shorten a text
  • Rewrite in plain language
  • LinkedIn post
  • Job advertisement
  • Reply to a customer enquiry
  • Weigh pros and cons
  • Explain an Excel formula

Editing and deleting

On the Prompts page you change a prompt with Edit and remove it with Delete prompt. A deleted workspace prompt disappears for everyone. From the library inside a chat, Manage prompts takes you straight to this page.

Read next

Still have a question? Write to us.