do i really have to sign a paper just to walk through an open house?

You do not NEED to sign a representation agreement to tour an open house. There will typically be a disclosure for you to sign to cover both parties but some people sign those and some people don't. It is on display to cover the agent holding the open house.

Under the new rules tied to the National Association of Realtors settlement, a written buyer agreement is only required when an agent is actually working with you (showing homes, advising, writing offers, etc.), not when you’re casually attending an open house. At an open house, the agent is representing the seller, not you, so you should be able to walk through without signing anything. If someone is pushing a full buyer agreement at the door, that’s not the rule, you can politely decline and still view the home.

There have been changes regarding this and each state still does it a little differently. In PA, a buyer representation is required prior to showing a home; however, if it is an open house and the listing agent is showing it, they actually represent the seller. Therefore, in that situation, they should be able to show it to you without any documents signed, but again... this does differ by state.