> ## Documentation Index
> Fetch the complete documentation index at: https://cometchat-22654f5b-docs-agent-native-development.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Properties and Constraints

> Review CometChat Notification API properties and constraints for push, email, SMS, providers, preferences, and templates.

Properties and constraints for the Notification APIs.

## Push Notifications

| **Property** | **Constraints** |
| - | - |
| Maximum FCM providers per app | Contact support for limits |
| Maximum APNS providers per app | Contact support for limits |
| Maximum push tokens per user | 100 active tokens |
| Push token value | Max 4,096 characters |

## Email Notifications

| **Property** | **Constraints** |
| - | - |
| SendGrid API key | Required for SendGrid provider |
| Custom provider webhook URL | Must be a valid HTTPS URL |

## SMS Notifications

| **Property** | **Constraints** |
| - | - |
| Twilio Account SID | Required for Twilio provider |
| Twilio Auth Token | Required for Twilio provider |
| Custom provider webhook URL | Must be a valid HTTPS URL |


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