# Libraries and templates

> A library is a brand's governed kit of modules, settings and rules. A template is an approved starting layout inside it. Every email built through the MCP starts from one.

Source: https://stensul.com/developers/concepts/libraries-and-templates/ · Last reviewed 2026-09-28

## Libraries

A **library** holds everything one brand, region or team is allowed to build with: its modules, the settings each email may use, styling variations, languages, tags, tracking rules and connected integrations. People only see libraries their permissions include.

When your assistant calls `stensul-get-libraries` with a library key, it learns:

| It learns | Why it matters |
| --- | --- |
| The modules, by role, and which variations each supports | What it can place in an email |
| `subject_line_enabled`, `preheader_enabled`, `title_enabled` and their length caps | Which settings it may send. Sending a disabled one gets the whole call declined |
| The variations mode (`all` or `individual`) | Whether styling applies to the whole email or per module |
| `dca_segment_sets.supported` | Whether audience versions work in this library |
| Languages and tags | Valid values for new emails |

**Name libraries descriptively.** Assistants match your brief to library names. "EMEA Retail – German" beats "Lib 7".

## Templates

A **template** is an approved email layout: a fixed sequence of modules with starter content. Admins make templates in Stensul; the MCP can't create one from scratch. An email saved as a template can be copied to start new emails, but never becomes a sendable email itself.

## Two ways to start an email

```text
Template ──(template_id)──▶ new draft with the template's module order
Existing email ──(copy_of)──▶ new draft with its content and images
```

`stensul-build-email` takes exactly one of `template_id` or `copy_of`, then writes content **by position** against a read of that source: module 1 is the first module, element 2 is the second element in it. That's why a good assistant reads the source with `stensul-read-email` first.

If a library has no template and no email to copy, there's nothing to start from, and the assistant should say so rather than improvise.