# Get price change alerts from any Actor's dataset

**Use case:** 

Compares each run of a source Actor against its previous one and emits only the items whose price field changed, with old and new values, ignoring fields that move on their own like timestamps and rank. Add a Slack, Discord or Telegram webhook and the changes arrive as a message.

## Input

```json
{
  "source": "demo",
  "emit": [
    "changed"
  ],
  "watchFields": [
    "price"
  ],
  "notifyMaxItems": 20,
  "outputMode": "deltaOnly",
  "firstRunBehaviour": "baselineOnly",
  "ignoreFields": [
    "scrapedAt",
    "crawledAt",
    "timestamp",
    "position",
    "rank"
  ],
  "maxItems": 50000
}
```

## Output

```json
{
  "_change": {
    "label": "Change"
  },
  "_key": {
    "label": "Item key"
  },
  "_error": {
    "label": "Error"
  },
  "_changedFields": {
    "label": "Fields changed"
  },
  "_previousValues": {
    "label": "Previous values"
  },
  "_source": {
    "label": "Source"
  },
  "_seenAt": {
    "label": "Seen at"
  }
}
```

## About this Actor

This example demonstrates how to use [Dataset Diff: Only New & Changed Items From Any Actor](https://apify.com/fayoussef/dataset-diff.md) with a specific input configuration. Visit the [Actor detail page](https://apify.com/fayoussef/dataset-diff.md) to learn more, explore other use cases, and run it yourself.


## How to integrate an Actor?

This Task's input is already configured above. Use it as-is rather than inventing a new one.

Do not guess an integration path. Every one of them is in the agent quickstart at https://apify.com/agents.md: the Apify MCP server, Agent Skills with the Apify CLI, the JavaScript and Python clients, the REST API, and the account-free path for an agent with no human to sign in. It also carries the rule on stating cost before the first paid run.

For full API examples (JavaScript, Python, CLI, MCP, OpenAPI), see this Task's Actor page: https://apify.com/fayoussef/dataset-diff.md

Each client library has reference documentation the quickstart does not restate: [JavaScript/TypeScript](https://docs.apify.com/api/client/js/docs.md) (`npm install apify-client`) and [Python](https://docs.apify.com/api/client/python/docs.md) (`pip install apify-client`).