minor tweaks and new image

topics/dev/tutorials/tool-generators/tutorial.md

@@ -218,21 +218,39 @@ In this case, a single text string is needed from the user.
 
 Tool definition involves configuring the major sections of the ToolFactory form for the new tool.
 
-The following information about a script is needed:
+Five categories needed to generate a script:
 
 - Conda dependency requirements
 - History data inputs
-- History outputs - data and collections
+- History outputs
 - User controlled parameters
+- Developer supplied code/scripts to embed
 
 For the `hello` tool case:
 
+Conda dependency requirements:
+
 - There are no dependencies usually because bash is available and version is not important.
 - For completeness, it could be included as a Conda package. It's your tool.
+
+History data inputs:
+
 - This tool requires no history input files.
+
+History outputs - data and collections:
 - It produces one text output file.
+
+User controlled parameters:
 - The tool form should show a single input text field for the user to supply.
-- Executing the tool is expected to write the combined string to a new history item.
+
+Developer supplied code/scripts to embed:
+- These are optional - many Conda packages will not need them.
+- Most simple use-cases will involve developer supplied, known working code.
+- Executing the tool is expected to write the decorated string to a new history item.
+- This must be known to work with suitable inputs on the command line. 
+  - Broken code == broken tool.
+- Such as `echo "Hello $1!"` as a Bash script
+- There are other advanced features, such as command over-rides where code can be embedded
 
 At this point, the plan for this new tool is: