# Build Categories

You can use the `CategoryBuild` action to build a category. You must build a category after you create it and train it, as well as every time that you retrain it. Building a category identifies the concepts of the training for the category and indexes the category into the IDOL category index (IDOL Agentstore component). For example:

    action=CategoryBuild&Category=32349987602210557106

In this example, the IDOL Category component builds the category with the ID `32349987602210557106`.

NOTE: If you train or retrain a category by using the `CategorySetTraining` action with `BuildNow` set to `True`, you do not have to run a `CategoryBuild` action, because the category was built immediately after it was trained.

The IDOL Category component also builds categories immediately if you assign training parameters to the `CategoryCreate` action to train a category when you create it.

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