Again I tell you, if two of you on earth agree (harmonize together, make a symphony together) about whatever [anything and everything] they may ask, it will come to pass and be done for them by My Father in heaven. For wherever two or three are gathered (drawn together as My followers) in (into) My name, there I AM in the midst of them.
(Matthew 18:19-20, Amplified Bible)

When you have faith in God Almighty and the Lord Jesus Christ then you are in total agreement with Him. Faith means you trust and rely with total agreement on Him and His Word. In the Gospel of Mark 9:23, Jesus said to him, “If you can believe, all things are possible to him who believes.” When you pray in the name of Jesus you are coming into agreement with the Lord Jesus Christ! In John 14:13 Jesus says, “And whatever you ask in My name, that I will do, that the Father may be glorified in the Son. Whenever you pray in agreement with the Word of God then you are in agreement in your prayers with God Almighty, the Lord Jesus Christ and all of heaven!

Now this is the confidence that we have in Him, that if we ask anything according to His will, He hears us. And if we know that He hears us, whatever we ask, we know that we have the petitions that we have asked of Him.
(1 John 5:14-15)

In the Bible the Lord Jesus Christ would make sure the people coming to be healed or to receive their miracle were in agreement with Him. He would ask do you believe I am able to do this?

And when He had come into the house, the blind men came to Him. And Jesus said to them, “Do you believe that I am able to do this?” They said to Him, “Yes, Lord.” Then He touched their eyes, saying, “According to your faith let it be to you.”
(Matthew 9:28 -29)

The greatest prayer of agreement with the Lord Jesus Christ is when you pray in the Spirit. You then are praying the perfect will of God down on this world!

Now He who searches the hearts knows what the mind of the Spirit is, because He makes intercession for the saints according to the will of God.
(Romans 8:27)