Describing Metadata Types

The describeMetadata target returns a list of metadata types that are enabled for your organization. This target is useful when you want to identify the syntax needed for a metadata type in a <name> element in package.xml; for example, CustomObject for custom objects or Layout for page layouts. The following parameters may be set for each <sf:describeMetadata> target:

Field	Description
username	Required if sessionId isn’t specified. The Salesforce username for login. The username associated with this connection must have the “Modify All Data” permission. Typically, this is only enabled for System Administrator users.
password	Required if sessionId isn’t specified. The password you use to log into the organization associated with this project. If you are using a security token, paste the 25-digit token value to the end of your password.
sessionId	Required if username and password aren’t specified. The ID of an active Salesforce session. A session is created after a user logs in to Salesforce successfully with a username and password. Use a session ID for logging into an existing session instead of creating a new session.
serverurl	Optional. The Salesforce server URL (if blank, defaults to `login.salesforce.com`). To connect to a sandbox instance, change this to `test.salesforce.com`.
apiVersion	Optional. The API version to use for the metadata. The default is 36.0.
resultFilePath	Optional. The path of the output file where results are stored. The default output is the console. Directing the output to a file makes it easier to extract the relevant information for your package.xml manifest file.
trace	Optional. Defaults to `false`. Prints the SOAP requests and responses to the console. Note that this will show the user's password in plain text during login.

To get the list of metadata types enabled for your organization, specify a target in the build.xml file using <sf:describeMetadata>.

1<target name="describeMetadata">
2  <sf:describeMetadata
3    username="${sf.username}"
4    password="${sf.password}"
5    sessionId="${sf.sessionId}"
6    serverurl="${sf.serverurl}"
7    resultFilePath="describeMetadata/describe.log"/>
8</target>

Force.com Migration Tool Guide

Describing Metadata Types