Engineering Expert

Through dedicated study, practical experience, and time, you have gained an expert level understanding of Engineering, granting you additional benefits from your tool usage:

• Increase your Intelligence score by 1, to a maximum of 20.
• You gain proficiency and expertise with Tinker's Tools, Mason's Tools, Carpenter's Tools, and Smith's Tools if you don't already have it. Expertise means your proficiency bonus is doubled for the ability check.
• Additionally, when you use any of these tool proficiencies for the purpose of gaining either Advantage or for an Added Benefit on ability check using a skill with which you are proficient (p78, XgtE - "Tools and Skills Together"). You are considered to have expertise with that skill for this check only, if you are not proficient in that skill your proficiency bonus is only added once.   
• An example of this would be, an expert Mason would be able to Investigate to determine weak points in a stone structure, if they are proficient in the Investigation skill, they would gain expertise for that skill check, if they were not proficient in the required skill, they would only add their proficiency bonus once.