By supporting tools, I mean:

• reference data manager, like virus definition for anti-virus software
• test data generator
• level builders for games
• simulators or advanced mocking systems

Does the team building the core product (in the case above, the game or the anti-virus) should be part of the development of the supporting tools significantly, or this is a task you would outsourced out of the team to help it focus on the product?

I don't have enough experience to evaluate the pros & cons of each, so I'm hopping you would come up with personal experiences to share, or even studies or papers you read on the subject.