How to add further info (desc, image, date) to a tag list in Eleventy

I'm working on a portfolio using Eleventy,

I've created a pagination for the tags with the following code

    ---
pagination:
  data: collections
  size: 1
  alias: tag
  addAllPagesToCollections: true
layout: blog
permalink: /blog/tag/{{tag | slugify }}/index.html
eleventyComputed:
  title: "{{ tag }}"
---

<br>
<p style= "font-size:22px">Entradas con la etiqueta: <strong>{{ tag }}</strong></p><br>

{% for post in collections[tag] %}
  <li>
    <a href="{{post.url}}" style="color:blue">{{post.data.title}}</a>
  </li>
{% endfor %}

This is fine enough but I wanted to see if it's possible to make the listed items display other data from the front matter like the desc, date and preview image

Try using post.data.desc or post.data.date, etc. Add those to your paginated template and see what shows up.