The following code are to be included in the header of your Tumblr theme:
{Title} – The html title of your blog
{Meta Description} – An html description of your blog for use within the meta tag
{Favicon} – A dynamically generated favicon url from your portrait photo
{RSS} – The url to the RSS feed of your tumbleblog
The following code is for your profile picture on your Tumblr:
{PortraitURL-64} – Different sizes are available (16, 24, 30, 40, 48, 64, 96, 128)
The following code is to be used where different types of posts will be displayed:
{block:Text}{/block:Text} – Displays Text posts
{block:Photo}{/block:Photo} – Displays Photo posts
{block:Photoset}{/block:Photoset} – Displays Photoset posts
{block:Quote}{/block:Quote} – Displays Quote posts
{block:Link}{/block:Link} – Displays Link posts
{block:Chat}{/block:Chat} – Displays Chat posts
{block:Audio}{/block:Audio} – Displays Audio posts
{block:Video}{/block:Video} – Displays Video posts
{block:Answer}{/block:Answer} – Displays answer posts
{Permalink} – The exact url for a single post
{ShortURL} – The sharing friendly short url for a single post
{PostID} – The unique numeric post ID for a single post
The following code is to be used for the Next/Previous links:
{block:Pagination}{/block:Pagination} – Only displays if there are previous / next pages to link to
{block:PreviousPage}{/block:PreviousPage} – Only displays if there is a previous page
{block:NextPage}{/block:NextPage} – Only displays if there is a next page
{PreviousPage} – Url for the previous page
{NextPage} – Url for the next page
{block:PermalinkPagination}{/block:PermalinkPagination} – Only displays if there are previous / next posts
{block:PreviousPost}{/block:PreviousPost} – Only displays if there is a previous post
{block:NextPost}{/block:NextPost} – Only displays if there is a next post
{PreviousPost} – Url for the previous post
{NextPost} – Url for the next post
Additional Resource: freecodesource.com