Adds one or more tags to an IAM user. If a tag with the same key name already exists, then that tag is overwritten with the new value.

A tag consists of a key name and an associated value. By assigning tags to your resources, you can do the following:

• Administrative grouping and discovery - Attach tags to resources to aid in organization and search. For example, you could search for all resources with the key name Project and the value MyImportantProject. Or search for all resources with the key name Cost Center and the value 41200.
• Access control - Include tags in IAM user-based and resource-based policies. You can use tags to restrict access to only an IAM requesting user that has a specified tag attached. You can also restrict access to only those resources that have a certain tag attached. For examples of policies that show how to use tags to control access, see Control access using IAM tags in the IAM User Guide.
• Cost allocation - Use tags to help track which individuals and teams are using which Amazon Web Services resources.
• If any one of the tags is invalid or if you exceed the allowed maximum number of tags, then the entire request fails and the resource is not created. For more information about tagging, see Tagging IAM resources in the IAM User Guide.
• Amazon Web Services always interprets the tag Value as a single string. If you need to store an array, you can store comma-separated values in the string. However, you must interpret the value in your code.

For more information about tagging, see Tagging IAM identities in the IAM User Guide.