# Using Custom Instructions
Learn how to use and override model instructions in Minibase Ollama.
## What Are Instructions?
Instructions tell your model what task to perform. Every Minibase model has a **default instruction** from training.
## Default Instructions
Your model's default instruction is automatically applied. For example, a toxic text removal model might have:
```
"Rewrite the provided text to remove the toxicity."
```
When you run:
```bash
echo "fuck you" | ollama run my-model
```
The model actually receives:
```
Instruction: Rewrite the provided text to remove the toxicity.
Input: fuck you
Response:
```
## Custom Instructions
Override the default with `--instruction`:
```bash
echo "fuck you" | ollama run my-model --instruction "Make the text polite"
# Output: "I respectfully disagree"
```
## Common Use Cases
### Change Task
```bash
# Default: Remove toxicity
echo "Hello world" | ollama run my-model
# Custom: Translate
echo "Hello world" | ollama run my-model --instruction "Translate to Spanish"
```
### Change Output Format
```bash
# Default: Natural language
echo "This is spam" | ollama run my-model
# Custom: JSON format
echo "This is spam" | ollama run my-model --instruction "Classify as spam/not-spam. Respond in JSON format."
```
### Add Constraints
```bash
# Custom: Limit length
echo "Long text..." | ollama run my-model --instruction "Summarize in under 10 words"
```
## Best Practices
**DO:**
* Be specific: "Translate to Spanish" not "translate this"
* Specify format: "Respond in JSON with keys: result, confidence"
* Add constraints: "Summarize in 2 sentences"
**DON'T:**
* Be vague: "make it better"
* Expect tasks the model wasn't trained for
* Use overly long instructions (keep under 100 words)
## Examples
### Content Moderation
```bash
echo "bad text" | ollama run my-model --instruction "Rate toxicity from 1-10"
```
### Classification
```bash
echo "email text" | ollama run my-model --instruction "Classify as: spam, phishing, or legitimate"
```
### Data Extraction
```bash
echo "John at [email protected]" | ollama run my-model --instruction "Extract email addresses"
```
## View Default Instruction
```bash
ollama show YOUR_MODEL_ID --modelfile
```
Look for the `SYSTEM` line - that's your default instruction.
## More Information
* [Ollama Modelfile Documentation](https://github.com/ollama/ollama/blob/main/docs/modelfile.md)
* [Prompt Engineering Guide](https://www.promptingguide.ai/)