Add package summary

README.md

@@ -1,7 +1,20 @@
 scDiagnostics: diagnostic functions to assess the quality of cell type
-assignments in single-cell RNA-seq
+annotations in single-cell RNA-seq data
 ================
 
+# Purpose
+
+Annotation transfer from a reference dataset for the cell type annotation of a new query single-cell RNA-sequencing (scRNA-seq) experiment
+is an integral component of the typical analysis workflow. The approach provides a fast, automated, and reproducible alternative to the 
+manual annotation of cell clusters based on marker gene expression. However, dataset imbalance and undiagnosed incompatibilities between
+query and reference dataset can lead to erroneous annotation and distort downstream applications. 
+
+The `scDiagnostics` package provides functionality for the systematic evaluation of cell type assignments in scRNA-seq data.
+`scDiagnostics` offers a suite of diagnostic functions to assess whether both (query and reference) datasets are aligned,
+ensuring that annotations can be transferred reliably. `scDiagnostics` also provides functionality to assess annotation ambiguity, cluster
+heterogeneity, and marker gene alignment. The implemented functionality helps researchers to determine how accurately cells from a new scRNA-seq
+experiment can be assigned to known cell types.
+
 # Installation
 
 To install the development version of the package from GitHub use the following command: