How can I get the arguments and types of graphql mutations via introspection?

If you would like to get the arguments of a specific mutation, you can use an introspection query to get its InputObject type.

Say you have a create user mutation that looks something like this

mutation createUser($input: CreateUserInput!) {
  create_user(input: $input) {
    user {
     id
     name
    }
  }
}

You can then use an introspection query to get the CreateUserInput

query createUserInput {   
  __type(name: "CreateUserInput") {
    name
    inputFields {
      name
      description
      defaultValue
    }
  }
}

and use the inputFields from that query to see the mutations arguments. gql introspection docs