As part of a review of all job descriptions, my company has decided to include the following as a key output:website development completed on  time, within specification and error  freeGiven that specifications regularly change, there is no formal change control process and environments are, shall we say, a little unpredictable, how realistic and reasonable is this KPI?
Is it appropriate in a developer's job description to have error free as a key output?
terminology;performance;employment
Error Free is far too subjective.  One man's Unfufilled feature request is another man's Error.  Something like Should substantially meet design specs would be more appropriate.  I've never actually seen what you describe in a job description.  I've seen it for contract work, but not for employees.