I have developed my personal agentic file format `.ag` for this purpose.

Here is the template I start with:

    #!/usr/bin/env gpt-agent
     
    input: <target/context (e.g., cwd)>
     
    task: |
      <one clear objective>
     
    output: |
      <deliverables + required format>
     
    require:
      - <must be true before start; otherwise stop + report>
     
    invariant:
      - <must stay true while working (scope + safety)>
     
    ensure:
      - <must be true at the end (definition of done)>
     
    rescue: |
      <what to do if any requirement/invariant/ensure cannot be met>