JSONNET

JSONNET is a data templating language that extends JSON with variables, conditionals, and functions. SuprSend uses JSONNET as the templating language for rich Slack Block Kit and MS Teams Adaptive Card templates. All trigger payload data, recipient properties, tenant properties, and batched event data are available under the data object.

Variable syntax

Variable type	Syntax	Example
Top-level key	`data.key`	`data.order_id`
Nested object	`data.parent.child`	`data.order.address.city`
Special characters or spaces in key	`data['key']`	`data['$recipient'].name`, `data.event['first name']`
Array element at index	`data.array[index]`	`data.items[0].product_name`
Recipient property	`data['$recipient'].key`	`data['$recipient'].name`
Actor property	`data['$actor'].key`	`data['$actor'].name`
Tenant property	`data['$brand'].key`	`data['$brand'].brand_name`
Batched event count	`data['$batched_events_count']`
Batched event item	`data['$batched_events'][0].key`	`data['$batched_events'][0].title`

The {{variable}} Handlebars syntax does not work in JSONNET editors. Use data.key syntax only. Similarly, the Adaptive Card ${variable} syntax is not supported - use data.key instead.

Iterating over arrays

Use JSONNET for loops to repeat blocks for each item in an array:

{
  "blocks": [
    {
      "type": "section",
      "fields": [
        {
          "type": "plain_text",
          "text": item.name + ": " + item.description
        }
        for item in data.items
      ]
    }
  ]
}

For batched events (from batch or digest nodes):

{
  "blocks": [
    {
      "type": "section",
      "fields": [
        {
          "type": "plain_text",
          "text": event.title + " (" + event.status + ")"
        }
        for event in data["$batched_events"]
      ]
    }
  ]
}

Conditional logic

Use if/then/else for conditional content:

{
  "type": "section",
  "text": {
    "type": "mrkdwn",
    "text": if "is_new_org" in data then
      "New Organization"
    else
      "Existing Organization"
  }
}

String formatting

JSONNET supports Python-style string interpolation with %:

{
  "type": "section",
  "text": {
    "type": "mrkdwn",
    "text": "*<%(link)s|%(name)s>* requested by %(requester)s" % {
      link: data.document_link,
      name: data.document_name,
      requester: data.requester_name
    }
  }
}

Or use string concatenation with +:

"text": "Order " + data.order_id + " has shipped to " + data['$recipient'].name

Slack Block Kit examples

Design visually in the Slack Block Kit Builder, then adapt the JSON into JSONNET by replacing hardcoded values with data.key references.

Slack templates must be wrapped in {"blocks": [...]}.The SuprSend JSONNET editor for Slack only accepts the {"blocks": [...]} object format. A bare array (e.g., [{"type": "section", ...}]) will not render - wrap your blocks inside a top-level object with a blocks key.The Block Kit Builder also outputs this {"blocks": [...]} shape by default, so you can copy its output directly and replace hardcoded values with data.key references.

Simple text notification

{
  "blocks": [
    {
      "type": "section",
      "text": {
        "type": "mrkdwn",
        "text": "New Signup on ABC company"
      }
    },
    {
      "type": "section",
      "text": {
        "type": "mrkdwn",
        "text": ">_UserName_: *%(user_name)s*\n>_Email_: *%(email)s*\n>_Organization_: *%(org_name)s*\n>_Domain_: *%(domain)s*" % {
          user_name: data.user_name, 
          email: data.user_email, 
          org_name: data.org.name, 
          domain: data.org.domain
        }
      }
    },
    {
      "type": "divider"
    }
  ]
}

{
  "user_name": "John Doe",
  "user_email": "john@doe.com",
  "org": {
    "name": "ABC company",
    "domain": "abc.com"
  }
}

Approval request with buttons

{
  "blocks": [
    {
      "type": "section",
      "text": {
        "type": "mrkdwn",
        "text": "Share access requested for *<%(document_link)s|%(document_name)s>*" % {
          document_link: data.document_link,
          document_name: data.document_name
        }
      }
    },
    {
      "type": "section",
      "fields": [
        {
          "type": "mrkdwn",
          "text": "*Requested by:*\n" + data.requester_name
        },
        {
          "type": "mrkdwn",
          "text": "*When:*\n" + data.submitted_at
        },
        {
          "type": "mrkdwn",
          "text": "*Reason:*\n" + data.access_reason
        }
      ]
    },
    {
      "type": "actions",
      "elements": [
        {
          "type": "button",
          "text": { "type": "plain_text", "text": "Approve" },
          "style": "primary",
          "value": "approve_access"
        },
        {
          "type": "button",
          "text": { "type": "plain_text", "text": "Deny" },
          "style": "danger",
          "value": "deny_access"
        }
      ]
    }
  ]
}

{
  "access_type": "View",
  "submitted_at": "Jul 14, 2025",
  "access_reason": "Need to review figures before tomorrow's board meeting.",
  "document_link": "https://docs.company.com/12345",
  "document_name": "Q3 Financial Report",
  "requester_name": "Jane Doe"
}

Anomaly alert with image

{
  "blocks": [
    {
      "type": "section",
      "text": {
        "type": "mrkdwn",
        "text": ":warning: *High Error Rate Detected*\nOur system has experienced a spike in errors over the last *30 minutes*."
      }
    },
    {
      "type": "image",
      "title": { "type": "plain_text", "text": "Request vs Failure Trend (Last 6 Hours)" },
      "image_url": data.image_url,
      "alt_text": "Graph showing high error rate spike"
    },
    {
      "type": "section",
      "fields": [
        { "type": "mrkdwn", "text": "*Impacted Services:*\n" + data.impacted_services },
        { "type": "mrkdwn", "text": "*Error Rate:*\n" + data.error_rate }
      ]
    },
    {
      "type": "context",
      "elements": [
        {
          "type": "mrkdwn",
          "text": ":mag: View logs: <%(log_url)s|Open in Monitoring Tool>" % { log_url: data.log_url }
        }
      ]
    }
  ]
}

{
  "log_url": "https://monitoring.company.com/logs",
  "image_url": "https://datadog-docs.imgix.net/images/dashboards/widgets/alert_graph/alert_graph.png",
  "error_rate": "17.2% (normally <1%)",
  "impacted_services": "API Gateway, Auth Service"
}

Batched task digest

{
  "blocks": [
    {
      "type": "section",
      "text": {
        "type": "mrkdwn",
        "text": "Hi " + data["$recipient"].name + " :wave:\nYou have " + data["$batched_events_count"] + " *pending tasks* for today:"
      }
    },
    {
      "type": "rich_text",
      "elements": [
        {
          "type": "rich_text_list",
          "style": "bullet",
          "elements": [
            {
              "type": "rich_text_section",
              "elements": [
                { "type": "text", "text": task.title + " (" + task.status + ")" }
              ]
            }
            for task in data["$batched_events"]
          ]
        }
      ]
    },
    {
      "type": "actions",
      "elements": [
        {
          "type": "button",
          "text": { "type": "plain_text", "text": "View Pending tasks" },
          "url": "https://app.company.com/tasks"
        }
      ]
    }
  ]
}

{
  "$batched_events_count": 3,
  "$batched_events": [
    { "title": "Fix login bug on mobile", "status": "In Progress" },
    { "title": "Write API docs for new endpoints", "status": "Todo" },
    { "title": "Review design spec for onboarding", "status": "Blocked" }
  ]
}

MS Teams Adaptive Card examples

Design visually in the Adaptive Cards Designer, then adapt the JSON into JSONNET.

Approval request with FactSet and buttons

{
  "$schema": "http://adaptivecards.io/schemas/adaptive-card.json",
  "type": "AdaptiveCard",
  "version": "1.6",
  "body": [
    {
      "type": "TextBlock",
      "text": "Expense Report Approval",
      "weight": "Bolder",
      "size": "Medium"
    },
    {
      "type": "FactSet",
      "facts": [
        {"title": "Submitted by", "value": data.requester_name},
        {"title": "Amount", "value": data.amount},
        {"title": "Category", "value": data.category},
        {"title": "Date", "value": data.submitted_date}
      ]
    }
  ],
  "actions": [
    { "type": "Action.OpenUrl", "title": "Approve", "url": data.approve_url },
    { "type": "Action.OpenUrl", "title": "Reject", "url": data.reject_url }
  ]
}

Use FactSet for key-value data and Action.OpenUrl for CTA buttons.

Dynamic list with for loop

{
  "$schema": "http://adaptivecards.io/schemas/adaptive-card.json",
  "type": "AdaptiveCard",
  "version": "1.6",
  "body": [
    {
      "text": product.name + " at " + product.price,
      "type": "TextBlock",
      "wrap": true
    }
    for product in data.products
  ]
}

Debugging

Preview not loading - ensure all data.key variables have values in the Variables panel. Missing mock data causes render errors.
Syntax error in preview - check for missing commas, unmatched brackets, or using {{}} instead of data.key.
Slack message not rendering - make sure your template is wrapped in {"blocks": [...]}. A bare array ([...]) is not valid for the SuprSend Slack JSONNET editor.
Slack silently drops blocks - validate your output in the Block Kit Builder before committing.
Teams renders differently than designer - always test in an actual Teams chat. The Adaptive Cards Designer is an approximation, not exact.

AI prompt - debug JSONNET: “Fix this JSONNET error from the SuprSend editor. Error: [paste error]. Code: [paste JSONNET]. Variables are accessed as data.key or data[‘$special_key’].”

GETTING STARTED

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MANAGE YOUR ACCOUNT

Variable syntax

Iterating over arrays

Conditional logic

String formatting

Slack Block Kit examples

MS Teams Adaptive Card examples

Debugging

​Variable syntax

​Iterating over arrays

​Conditional logic

​String formatting

​Slack Block Kit examples

​MS Teams Adaptive Card examples

​Debugging

Variable syntax

Iterating over arrays

Conditional logic

String formatting

Slack Block Kit examples

MS Teams Adaptive Card examples

Debugging