# MCP Tool Contract: preview-iteration
## Overview
Preview uma iteração específica sem alterar o estado da sessão (operação não-destrutiva).
## Tool Name
`preview-iteration`
## Description
Preview a specific iteration without changing session state (non-destructive)
## Input Parameters
| Parameter | Type | Required | Description |
|-----------|------|----------|-------------|
| `sessionId` | string | Yes | Session identifier |
| `iterationIndex` | number | Yes | 0-based index of iteration to preview |
## Output Schema
```typescript
{
status: 'success' | 'error',
data?: {
index: number,
prompt: string,
image: string, // base64 encoded
dimensions: {
width: number,
height: number
},
parameters: Record<string, any>,
metadata: {
generationTime: number, // milliseconds
model: string,
seed?: number
},
timestamp: string
},
error?: string
}
```
## Use Cases
- **Review before rollback**: Preview iteration 3 to check prompt before deciding to rollback to it
- **Quick lookup**: Inspect specific iteration details without modifying session history
- **Parameter review**: Check what parameters were used in a specific generation
- **Image inspection**: View image without committing to rollback
## Notes
- Read-only operation, does not modify session state
- Does not trigger rollback or undo operations
- Faster than rollback + undo workflow when just inspecting
- Returns complete iteration metadata including generation info
- Non-destructive, can be called multiple times without side effects
## Error Handling
- Invalid sessionId → error status with message
- iterationIndex out of bounds → error status with message
- Session data corrupted or unavailable → error status with message
