Hi, hopefully you'll find the responsibilities of your work role outlined and explained in your job contract.
http://www.silkysteps.com/forum/showthread.php?t=16449
The boundaries of competence can be evaluted through looking at your strengths and weaknesses - what you do well and confidently and what you feel less able doing eg. a particular qualification would imply a level of competence as would a specialism or focussed interest.
page 37 of the heinemann handbook looks of competency (sill, knowledge or experience) as an individual's ..
Knowledge and experience of working with children of different ages, with different needs and in different settings.
Your skill at observing, planning and record keeping
How well you build positive relationships with parents, and how you work in partnership with parents.
Professional knowledge of curriculum frameworks
What you feel your people and leadership skills are like
How you manage a budget
What your information, communication and technology skills are
Writing skills - letters, reports, newsletters eg. spelling, grammar, comprehension, computer programme knowledge, creativity
Health and safety
Knowledge of legislation that affects the sector
Multi-agency working
Hth xx