The lono summary command helps you quickly understand a CloudFormation template.

Examples

$ bundle exec lono summary ec2
Generating CloudFormation templates for blueprint ec2:
  output/ec2/templates/ec2-old.yml
  output/ec2/templates/ec2-new.yml
=> CloudFormation Template Summary for template ec2-new:
Required Parameters (0):
  There are no required parameters.
Optional Parameters (3):
  InstanceType (String) Default: t3.micro
  Subnet (String) Default:
  Vpc (String) Default:
Resources:
  1 AWS::EC2::Instance
  1 AWS::EC2::SecurityGroup
  2 Total
=> CloudFormation Template Summary for template ec2-old:
Required Parameters (0):
  There are no required parameters.
Optional Parameters (3):
  InstanceType (String) Default: t3.micro
  Subnet (String) Default:
  Vpc (String) Default:
Resources:
  1 AWS::EC2::Instance
  1 AWS::EC2::SecurityGroup
  2 Total
$

Blog Post also covers this: lono summary Tutorial Introduction