When pledges are being negotiated, the Wyrd pays careful attention to the words that are spoken. Any pledge component spoken aloud becomes binding and subject to explicit agreement from both parties.
Pledges between two changelings must always have their components spelled out by both parties, often as an official document.
Pledges between a changeling and a human allow much more leeway to the changeling, as they get to decide what the human knows. When being sworn, any components not said aloud can be decided by the changeling alone. The only thing absolutely required is the human's agreement, which counts even if it's under false pretenses.