Cloud mta build tool document update (#1024)

* modified:   docs/docs/index.md

* modified:   docs/docs/index.md

* modified:   docs/docs/index.md

* modified:   docs/docs/index.md

* modified:   docs/docs/index.md

* modified:   docs/docs/index.md

* modified:   docs/docs/index.md

* modified:   docs/docs/index.md

Co-authored-by: Young Yang <young.yang03@sap.com>

Author: young-yang03

docs/docs/index.md

@@ -30,6 +30,13 @@ If the MTA Build Tool encounters a module type in the `mta.yaml` file that is no
 
 All resource definitions are passed to the `mtad.yaml` file as is without mapping and validations (for example, if the resource is supported in the target platform or if the specified parameters match the type).
 
-### <b>Creating an MTA Archive According to the MTA Deploymnet Descriptor (`mtad.yaml` file)</b>
+### <b>Creating an MTA Archive According to the MTA Deployment Descriptor (`mtad.yaml` file)</b>
+
+The function is provided to assemble multiple modules, which are developed and prebuilt as separate projects, into one MTAR for deployment. The function is implemented by the `mbt assemble` command, which copies all modules, module required dependencies, module build artifacts, and resource definitions into an MTAR, according to the MTA Deployment Descriptor (mtad.yaml file).
+
+If a module doesn’t have the `path` attribute, the assemble process skips it. If a module has the `path` attribute, but its value is invalid, the assemble process fails with the following error: `ERROR could not copy MTA artifacts to assemble: the "<path value>" path does not exist in the MTA project location`.
+
+If a required dependency or resource doesn’t have the `parameters.path` attribute, the assemble process skips it. If a required dependency or resource has the `parameters.path` attribute, but its value is invalid, the assemble process fails with the following error: `ERROR could not copy MTA artifacts to assemble: the "<parameters.path value>" path does not exist in the MTA project location`.
+
+For more details about how to use the MBT assemble command, see [How to build an MTA archive from the modules' build artifacts](https://github.com/SAP/cloud-mta-build-tool/blob/master/docs/docs/usage.md#how-to-build-an-mta-archive-from-the-modules-build-artifacts).
 
-Under construction