Name and description
A meaningful name and description for the parameters helps your clients understand and provide appropriate values for the parameter. By default, the Service Editor copies the description of the parameter from the tool's item description.
Type
The parameter type defines whether the client must supply a value for the task to execute successfully. In the Service Editor, you can only change optional parameters to required. To change a required parameter to an optional parameter, you'll need to exit the Service Editor, edit the properties of your tool, and run the tool again to create a new result.
Input mode
The Input mode determines how clients will input rasters to your task. There are three choices, described in detail below.
User defined value
In this mode, the client will use their own raster datasets as input to the task parameter. The Default value will always appear as <empty> as raster dataset parameters do not have a default value.
Choice list
Use the Choice list input mode when you want the client to choose one (or more) raster layers as input. The list of layers is populated from the applicable layers in the current map document. Check the box next to the layer or layers the client can choose as input.
Note:
You cannot add new layers or change their names in the Service Editor. Remove your task from the Service Editor, add or rename layers in the table of contents, then click Add Result 
, and add the result you previously removed. You'll see the changes you made to the table of contents.
Default value
The default value is the value of the parameter used to create the result. If the tool accepts multiple layers, then the default value can also be a list of layers, each layer separated by a semicolon. If the client fails to specify a value for the parameter, the task executes using the default value.
Note:
You cannot change the default value in the Service Editor. To change the value, exit the Service Editor and create a new result with the values you want to have as the default values.
Constant value
Use the Constant value mode when you want the task parameter to be fixed to a constant value.
- The value used for the Constant value is always the parameter value used to create the result. To change this value, you must create a new result with the desired value and publish the new result.
- Parameters with an input mode of Constant value do not become task parameters in the published task since clients cannot change their value.
- In this mode, the raster datasets become project data used by the task.