Child Protective Services (CPS) investigations must adhere to constitutional rights, and certain actions without proper legal justification can be deemed unconstitutional. The 7th Circuit Court of Appeals in Doe et al. v. Heck et al (No. 01-3648, 2003 US App. Lexis 7144) ruled that interviewing a child on private property without consent, a warrant, probable cause, or exigent circumstances violates the 4th and 14th Amendments.
Parents and caregivers should be aware of their rights during CPS investigations. CPS cannot enter a home or interview children without consent unless there is a warrant, an emergency, or the child is in immediate danger.
https://www.brettpritchardlaw.com/blog/2021/march/what-are-my-rights-during-a-child-protective-ser/
CPS must investigate all claims, even if they are false, but anonymous calls do not automatically provide probable cause.