Akshay Parkhi's Weblog

1) Prompt (Runtime System Prompt)

What it is: Instructions passed in the API call for a single request.

• One-time instruction (per request)
• Not enforced; the LLM may skip or reorder steps
• Good for quick control (tone, format, role)

Use when: prototyping, low-risk tasks, or temporary behavior changes.

Avoid when: you need guaranteed step execution or strict sequencing at scale.

2) Skill (Reusable Structured Prompt Module)

What it is: A reusable, structured reasoning template/module that improves consistency across repeated tasks.

• Reusable and standardized
• More consistent than ad-hoc prompts
• Still LLM-driven (probabilistic), not a hard execution engine

Use when: the task repeats often and you want consistent analysis structure, formatting, or output schema.

Avoid when: the workflow must never skip steps or must follow an exact sequence every time.

3) Tool (Deterministic Capability)

What it is: An executable function that performs a real action (API call, database query, file write, etc.).

• Deterministic execution (given correct code and inputs)
• Interacts with real systems or data
• Auditable and testable

Use when: you need real data, guaranteed operations, and repeatable correctness.

Important: Orchestrator (Code) for Strict Multi-Step Workflows

If your process requires a fixed sequence of steps that must always execute in order, the most reliable design is:

1. Use code (an orchestrator or state machine) to enforce the required steps deterministically.
2. Then pass the final combined results to the LLM for reasoning, optionally using a Skill for consistent formatting.

Quick Decision Rule

• Need guaranteed execution? Use Tools + Orchestrator.
• Need consistent repeated reasoning/output? Use a Skill.
• Need a one-off behavior tweak? Use a Prompt.