The BDB XML shell has a built in help facility, simply type help at the command line:

dbxml> help

Command Summary
---------------

#                - Comment. Does nothing
abort            - Aborts the current transaction
addAlias         - Add an alias to the default container
addIndex         - Add an index to the default container
append           - Append to nodes specified in the query expression
commit           - Commits the current transaction, and starts a new one
contextQuery     - Execute query expression using the last results as the 
     context item
cquery           - Execute an expression in the context of the default 
     container
createContainer  - Creates a new container, which becomes the default 
     container
debug            - Debug command -- internal use only
delIndex         - Delete an index from the default container
getDocuments     - Gets document(s) by name from default container
getMetaData      - Get a metadata item from the named document
help             - Print help information.  Use 'help commandName' for 
     extended help
info             - Get info on default container
insertAfter      - Insert new content after nodes selected by the query 
     expression
insertBefore     - Insert new content before nodes selected by the query 
     expression
listIndexes      - List all indexes in the default container
lookupEdgeIndex  - Performs an edge index lookup in the default container
lookupIndex      - Performs an index lookup in the default container
lookupStats      - Look up index statistics on the default container
openContainer    - Opens a container, and uses it as the default container
preload          - Pre-loads (opens) a container
print            - Prints most recent results, optionally to a file
putDocument      - Insert a document into the default container
query            - Execute an expression in the context of the XmlManager
queryPlan        - Prints the query plan for the specified query 
     expression
quit             - Exit the program
reindexContainer - Reindex a container, optionally changing index type
removeAlias      - Remove an alias from the default container
removeContainer  - Removes a container
removeDocument   - Remove a document from the default container
removeNodes      - Remove content from documents specified by the query 
     expression
renameNodes      - Rename nodes specified by the query expression
run              - Runs the given file as a script
setApplyChanges  - Modifies "apply changes" state in the default update 
     context
setBaseUri       - Set the base uri in the default context
setLazy          - Sets lazy evaluation on or off in the default context
setMetaData      - Set a metadata item on the named document
setNamespace     - Create a prefix->namespace binding in the default 
     context
setReturnType    - Sets the return type on the default context
setTypedVariable - Set a variable to the specified type in the default 
     context
setVariable      - Set a variable in the default context
setVerbose       - Set the verbosity of this shell
transaction      - Create a transaction for all subsequent operations to 
     use
updateNodes      - Update node content based on query expression and new 
     content
upgradeContainer - Upgrade a container to the current container format 

Any given command has additional detailed help. For example:

dbxml> help createContainer
            
createContainer -- Creates a new container, which becomes the default 
container

Usage: createContainer <containerName> [n|in|d|id] [[no]validate]
Creates a new default container; the old default is closed.
The default is to create a node storage container, with node indexes.
A second argument of "d" creates a Wholedoc storage container, and
"id" creates a document storage container with node indexes.
A second argument of "n" creates a node storage container, and
"in" creates a node storage container with node indexes.
The optional third argument indicates whether or not to validate
documents on insertion
A containerName of "" creates an in-memory container.
This command uses the XmlManager::createContainer() method.  

The help text has valuable information about the command and the API calls that are used to implement a particular command. This helps you to find the relevant section of the API documentation where more detail is available and also serves as a way to explore a commonly used subset of the API calls in an interactive fashion.