My foster children are staying with me but, if I had had to move them on, I imagine I would have told the following information:
What they are like academically/developmentally. Eg. If they are ahead of or behind their peers, or in the middle, any real strengths or weaknesses, any extra support they've had, how much progress they've made since coming into care etc.
What they were like with me in the early days as they may revert to this type of behaviour in the early days of adoption.
Any 'patterns' of behaviour. For example, with one of mine, if he sees too many professionals within a short space of time this can affect his behaviour at school as he starts to feel unsettled.
How they get on with other children and adults particularly when at parks and soft plays etc and family gatherings.
Any health issues they have/had - even if resolved, as they might resurface. Eg. One of mine was a bed wetter and the other one used to soil pants daily for a while when he was having problems at school.
Any concerns that the fc has about how the children will cope with moving on. In lots of cases they have had the children for months or years so will know the children well and will have suspicions about they will react.
Don't be put off, but be realistic about the issues you may encounter.