Set up Mattermost alerts

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Mattermost alerts reuse the same incoming-webhook payload format as Slack, so if you’ve set up Slack alerts before, this will look familiar. Under the hood a Mattermost contact is an http contact with its gateway set to Mattermost.

Settings reference

Setting (UI label)	API field (v2)	Type / allowed values	Default	Plan limits	What it does for you
Contact Type	`type`	`"http"`	-	-	Mattermost is stored as a plain `http` contact
Gateway	`gateway`	`"Mattermost"`	- (must be set explicitly)	-	Formats the request for Mattermost’s incoming-webhook shape
Webhook URL	`address`	Mattermost’s incoming-webhook URL	- (required)	-	Where the message posts
Group events	`groupedAlerts`	boolean	`false`	-	Combine simultaneous alerts into one message - see grouped alerts

Set it up in the app

In Mattermost, enable Incoming Webhooks (System Console → Integrations, if it isn’t already on) and create one for the channel you want alerts in. Copy the webhook URL.
In HostTracker, open Contacts and click Add contact.
Choose Mattermost.
Paste the webhook URL and give the contact a name.
Save.

What the message looks like

A formatted message in the target channel, using the same layout Slack alerts use - monitor name, status and detail fields, not a raw text blob.

Do it with the API or MCP

POST /contact
{ "type": "http", "gateway": "Mattermost", "address": "https://...", "name": "Ops Mattermost channel" }

MCP: use api_request with the body above - create_contact doesn’t cover http/gateway contacts.

What happens next

An http contact is born confirmed - there’s no code to verify. Send a test alert to confirm it actually posts.

Limits and gotchas

Alerts land in whichever channel the webhook is bound to - create another webhook in Mattermost for a second channel.
Grouping is off by default. Turn on the contact’s Group events toggle to combine simultaneous alerts into one message instead of posting them individually.
The gateway must be spelled exactly Mattermost; an unrecognized value is refused (422 unknown_enum_value) rather than silently treated as a plain webhook.
Being a recognized gateway also means Mattermost can receive certificate-expiry, domain-expiry, DNSBL blacklist and Web Risk notices - a plain unrecognized webhook contact cannot (see Webhook).