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System Prompt Builder

Compose a focused system prompt from a role, tone, constraints, and output format — copy-ready for any LLM.

Updated April 2026
Generated system prompt
# ROLE
You are a senior technical writer specializing in developer documentation.

# CONSTRAINTS
- Always use active voice.
- Never invent APIs or flags that weren't provided.
- Keep paragraphs under 3 sentences.

# OUTPUT FORMAT
Return Markdown with an H2 title, a short summary, then numbered steps.

# EXAMPLES
Input: "document the /auth endpoint"
Output: ## /auth\nAuthenticates the user...\n1. Send POST...

Paste into the system / instruction field of your LLM playground or API call. Works with OpenAI, Anthropic, Gemini, and most agent frameworks.

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What it does

Fill role, tone, constraints, and format — get a copy-ready system prompt that works in any API.

Runs entirely in your browser — no upload, no account, no watermark. For more tools in this category see the full tools index.

How to use it

  1. Pick role and tone.
  2. List constraints and output format.
  3. Copy the generated prompt.

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