Abstract: Degradable downhole tools, including degradable frac plugs, for use in combination with degradable delivery devices. Certain degradable delivery device embodiments contain one or more chemical additives that promote the complete dissolution of the degradable downhole tool. Certain degradable delivery device embodiments additionally or alternatively contain flowable sensors designed to measure operational conditions (e.g., pressure, temperature, pH, among others) within the wellbore to monitor the dissolution treatment and wellbore conditions. Certain degradable delivery device embodiments may be inserted into cavities of the degradable downhole tool prior to the tool being deployed in the wellbore and/or flowed into position near the deployed degradable downhole tool.