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Create a broadcast

create_broadcast

Destructive

Create a newsletter broadcast email for Kit subscribers with scheduling, templates, and audience filters. Requires confirm=true.

Instructions

Create a broadcast. May affect delivery, audience membership, published data or irreversible state. Requires confirm=true.

Input Schema

TableJSON Schema

Name	Required	Description
`public`	No	`true` to publish this broadcast to the web. The broadcast will appear in a newsletter feed on your Creator Profile and Landing Pages.
`account`	No	Named private account from KIT_ACCOUNTS. Defaults to KIT_DEFAULT_ACCOUNT or the first configured account.
`confirm`	No	Set true only when the user asked for exactly this action.
`content`	No
`payload`	No	Complete JSON body instead of individual body flags. Supports nullable fields and nested bulk structures. Cannot be combined with body flags or payload_file.
`send_at`	No	The scheduled send time for this broadcast in ISO8601 format. If no timezone is provided, UTC is assumed.
`subject`	No
`description`	No
`payload_file`	No	Local JSON request body file, at most 5 MB. Contents are validated before the API call and are never logged.
`preview_text`	No
`published_at`	No	The published timestamp to display in ISO8601 format. If no timezone is provided, UTC is assumed.
`email_address`	No	The sending email address to use. Uses the account's sending email address if not provided.
`thumbnail_alt`	No
`thumbnail_url`	No
`email_template_id`	No	Id of the email template to use. Uses the account's default template if not provided. 'Starting point' template is not supported.
`subscriber_filter`	No
`allow_starting_point`	No	Explicitly allow replacing a Starting point template body, as described in Kit’s current content-field documentation. Review the complete rendered HTML first.

Schema Changelog

Changes observed during successful MCP inspections.

Changed16 schema fields changedv3.0.0Oct 7, 2026

addedInput schema / $defs

Added value: +{
+  "all_item": {
+    "additionalProperties": false,
+    "properties": {
+      "ids": {
+        "items": {
+          "type": "integer"
+        },
+        "type": "array"
+      },
+      "type": {
+        "description": "`segment` or `tag`",
+        "enum": [
+          "segment",
+          "tag"
+        ],
+        "type": "string"
+      }
+    },
+    "required": [
+      "type",
+      "ids"
+    ],
+    "type": "object"
+  },
+  "content": {
+    "description": "The HTML content of the email. On a `Classic` template this is the body, and the template adds the design around it when the broadcast is sent. On a `Starting point` template the design lives in the body, so this is the complete email: keep the wrappers, images, inline styles and Liquid tags, including `{{ unsubscribe_url }}` and `{{ address }}`. Without an unsubscribe link the broadcast can't be sent. A read returns the string that was written, so `GET`, `PUT`, `GET` round-trips, apart from Kit's own \"Built with Kit\" badge, which a `Starting point` write takes out of the body and re-applies when the email renders. A broadcast built in Kit's editor reads back as Kit's rendered HTML instead, and writing that back replaces its individually-editable blocks with one HTML block. Sending `content` in the same request as a `Starting point` `email_template_id` also needs `allow_starting_point: true`. Omit `content` and name a `Starting point` template in `email_template_id` to create the broadcast with that template's own design.",
+    "type": "string"
+  },
+  "subscriber_filter": {
+    "description": "Filters your subscribers. At this time, we only support using only one filter group type via the API (e.g. `all`, `any`, or `none` but no combinations). If nothing is provided, will default to all of your subscribers.",
+    "items": {
+      "additionalProperties": false,
+      "minProperties": 1,
+      "properties": {
+        "all": {
+          "description": "Filters your subscribers using a logical AND of all provided segment and tag ids, i.e. a subscriber would have to be part of all segments and tags provided",
+          "items": {
+            "$ref": "#/$defs/all_item"
+          },
+          "type": "array"
+        },
+        "any": {
+          "description": "Filters your subscribers using a logical OR of all provided segment and tag ids, i.e. a subscriber would have to be part of at least one of the segments or tags provided",
+          "items": {
+            "$ref": "#/$defs/all_item"
+          },
+          "type": [
+            "array",
+            "null"
+          ]
+        },
+        "none": {
+          "description": "Filters your subscribers using a logical NOT of all provided segment and tag ids, i.e. a subscriber would have to be in none of the segments or tags provided",
+          "items": {
+            "$ref": "#/$defs/all_item"
+          },
+          "type": [
+            "array",
+            "null"
+          ]
+        }
+      },
+      "required": [
+        "all",
+        "any",
+        "none"
+      ],
+      "type": "object"
+    },
+    "type": "array"
+  }
+}

changedInput schema / properties / confirm / description

Previous value: -"Must be true for audience/delivery changes, publishing, destructive operations and signing-secret changes. Use only for an action requested by the user."New value: +"Set true only when the user asked for exactly this action."

addedInput schema / properties / content / $ref
```
Added value: +"#/$defs/content"
```

removedInput schema / properties / content / description

Removed value: -"The HTML content of the email. On a `Classic` template this is the body, and the template adds the design around it when the broadcast is sent. On a `Starting point` template the design lives in the body, so this is the complete email: keep the wrappers, images, inline styles and Liquid tags, including `{{ unsubscribe_url }}` and `{{ address }}`. Without an unsubscribe link the broadcast can't be sent. A read returns the string that was written, so `GET`, `PUT`, `GET` round-trips, apart from Kit's own \"Built with Kit\" badge, which a `Starting point` write takes out of the body and re-applies when the email renders. A broadcast built in Kit's editor reads back as Kit's rendered HTML instead, and writing that back replaces its individually-editable blocks with one HTML block. Sending `content` in the same request as a `Starting point` `email_template_id` also needs `allow_starting_point: true`. Omit `content` and name a `Starting point` template in `email_template_id` to create the broadcast with that template's own design."

removedInput schema / properties / content / type
```
Removed value: -"string"
```
addedInput schema / properties / payload / properties / content / $ref
```
Added value: +"#/$defs/content"
```

removedInput schema / properties / payload / properties / content / description

Removed value: -"The HTML content of the email. On a `Classic` template this is the body, and the template adds the design around it when the broadcast is sent. On a `Starting point` template the design lives in the body, so this is the complete email: keep the wrappers, images, inline styles and Liquid tags, including `{{ unsubscribe_url }}` and `{{ address }}`. Without an unsubscribe link the broadcast can't be sent. A read returns the string that was written, so `GET`, `PUT`, `GET` round-trips, apart from Kit's own \"Built with Kit\" badge, which a `Starting point` write takes out of the body and re-applies when the email renders. A broadcast built in Kit's editor reads back as Kit's rendered HTML instead, and writing that back replaces its individually-editable blocks with one HTML block. Sending `content` in the same request as a `Starting point` `email_template_id` also needs `allow_starting_point: true`. Omit `content` and name a `Starting point` template in `email_template_id` to create the broadcast with that template's own design."

removedInput schema / properties / payload / properties / content / type
```
Removed value: -"string"
```
addedInput schema / properties / payload / properties / subscriber_filter / $ref
```
Added value: +"#/$defs/subscriber_filter"
```

removedInput schema / properties / payload / properties / subscriber_filter / description

Removed value: -"Filters your subscribers. At this time, we only support using only one filter group type via the API (e.g. `all`, `any`, or `none` but no combinations). If nothing is provided, will default to all of your subscribers."

removedInput schema / properties / payload / properties / subscriber_filter / items

Removed value: -{
-  "additionalProperties": false,
-  "minProperties": 1,
-  "properties": {
-    "all": {
-      "description": "Filters your subscribers using a logical AND of all provided segment and tag ids, i.e. a subscriber would have to be part of all segments and tags provided",
-      "items": {
-        "additionalProperties": false,
-        "properties": {
-          "ids": {
-            "items": {
-              "type": "integer"
-            },
-            "type": "array"
-          },
-          "type": {
-            "description": "`segment` or `tag`",
-            "enum": [
-              "segment",
-              "tag"
-            ],
-            "type": "string"
-          }
-        },
-        "required": [
-          "type",
-          "ids"
-        ],
-        "type": "object"
-      },
-      "type": "array"
-    },
-    "any": {
-      "description": "Filters your subscribers using a logical OR of all provided segment and tag ids, i.e. a subscriber would have to be part of at least one of the segments or tags provided",
-      "items": {
-        "additionalProperties": false,
-        "properties": {
-          "ids": {
-            "items": {
-              "type": "integer"
-            },
-            "type": "array"
-          },
-          "type": {
-            "description": "`segment` or `tag`",
-            "enum": [
-              "segment",
-              "tag"
-            ],
-            "type": "string"
-          }
-        },
-        "required": [
-          "type",
-          "ids"
-        ],
-        "type": "object"
-      },
-      "type": [
-        "array",
-        "null"
-      ]
-    },
-    "none": {
-      "description": "Filters your subscribers using a logical NOT of all provided segment and tag ids, i.e. a subscriber would have to be in none of the segments or tags provided",
-      "items": {
-        "additionalProperties": false,
-        "properties": {
-          "ids": {
-            "items": {
-              "type": "integer"
-            },
-            "type": "array"
-          },
-          "type": {
-            "description": "`segment` or `tag`",
-            "enum": [
-              "segment",
-              "tag"
-            ],
-            "type": "string"
-          }
-        },
-        "required": [
-          "type",
-          "ids"
-        ],
-        "type": "object"
-      },
-      "type": [
-        "array",
-        "null"
-      ]
-    }
-  },
-  "required": [
-    "all",
-    "any",
-    "none"
-  ],
-  "type": "object"
-}

removedInput schema / properties / payload / properties / subscriber_filter / type
```
Removed value: -"array"
```
addedInput schema / properties / subscriber_filter / $ref
```
Added value: +"#/$defs/subscriber_filter"
```

removedInput schema / properties / subscriber_filter / description

Removed value: -"Filters your subscribers. At this time, we only support using only one filter group type via the API (e.g. `all`, `any`, or `none` but no combinations). If nothing is provided, will default to all of your subscribers."

removedInput schema / properties / subscriber_filter / items

Removed value: -{
-  "additionalProperties": false,
-  "minProperties": 1,
-  "properties": {
-    "all": {
-      "description": "Filters your subscribers using a logical AND of all provided segment and tag ids, i.e. a subscriber would have to be part of all segments and tags provided",
-      "items": {
-        "additionalProperties": false,
-        "properties": {
-          "ids": {
-            "items": {
-              "type": "integer"
-            },
-            "type": "array"
-          },
-          "type": {
-            "description": "`segment` or `tag`",
-            "enum": [
-              "segment",
-              "tag"
-            ],
-            "type": "string"
-          }
-        },
-        "required": [
-          "type",
-          "ids"
-        ],
-        "type": "object"
-      },
-      "type": "array"
-    },
-    "any": {
-      "description": "Filters your subscribers using a logical OR of all provided segment and tag ids, i.e. a subscriber would have to be part of at least one of the segments or tags provided",
-      "items": {
-        "additionalProperties": false,
-        "properties": {
-          "ids": {
-            "items": {
-              "type": "integer"
-            },
-            "type": "array"
-          },
-          "type": {
-            "description": "`segment` or `tag`",
-            "enum": [
-              "segment",
-              "tag"
-            ],
-            "type": "string"
-          }
-        },
-        "required": [
-          "type",
-          "ids"
-        ],
-        "type": "object"
-      },
-      "type": [
-        "array",
-        "null"
-      ]
-    },
-    "none": {
-      "description": "Filters your subscribers using a logical NOT of all provided segment and tag ids, i.e. a subscriber would have to be in none of the segments or tags provided",
-      "items": {
-        "additionalProperties": false,
-        "properties": {
-          "ids": {
-            "items": {
-              "type": "integer"
-            },
-            "type": "array"
-          },
-          "type": {
-            "description": "`segment` or `tag`",
-            "enum": [
-              "segment",
-              "tag"
-            ],
-            "type": "string"
-          }
-        },
-        "required": [
-          "type",
-          "ids"
-        ],
-        "type": "object"
-      },
-      "type": [
-        "array",
-        "null"
-      ]
-    }
-  },
-  "required": [
-    "all",
-    "any",
-    "none"
-  ],
-  "type": "object"
-}

removedInput schema / properties / subscriber_filter / type
```
Removed value: -"array"
```

First observedv2.0.1Oct 2, 2026

TDQS

B3.1/5.0

Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare destructiveHint=true, idempotentHint=false and openWorldHint=true, so the safety profile is covered structurally; the description nonetheless adds useful context by naming the affected surfaces (delivery, audience membership, published data, irreversible state) and the confirm gate. That is genuine added value beyond the annotations, though the phrasing "may affect" is vague about exactly what is destroyed.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Three short sentences, front-loaded with the action and the hard precondition, with no filler. It is efficiently written for the space it uses, though for a destructive 17-parameter tool the brevity edges toward under-specification.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness2/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

This is a destructive, open-world, non-idempotent create with a complex nested payload, no output schema, and no required fields — the description covers none of the practical requirements (e.g. that a subject/content or template is needed, how scheduling via send_at behaves, or what success looks like). Those gaps are significant relative to the tool's complexity.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters2/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

With 17 parameters, 0 required, nested objects, and schema coverage around 59% (including mutually-exclusive body flags vs `payload` vs `payload_file`), the description must compensate and does not. Its only parameter-level statement, "Requires confirm=true", merely repeats the `confirm` schema description. The complex `content`/`email_template_id`/`allow_starting_point` semantics are left entirely to the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose3/5

Does the description clearly state what the tool does and how it differs from similar tools?

The first sentence restates the title verbatim ("Create a broadcast"), and the tool name already conveys create + broadcast, so the description adds little about what a broadcast actually is or how it relates to siblings like create_sequence_email or update_broadcast. The action is unambiguous, but there is no field-level or scope detail beyond the title.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

"Requires confirm=true" is a real usage precondition, and the risk sentence hints that this is a consequential operation, so usage is implied rather than absent. However, there is no when-to-use/when-not-to-use guidance, no explanation of how to choose between the top-level body flags and the nested `payload` object, and no routing to the sibling update/delete broadcast tools.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

Deploy Server

Create a broadcast

Instructions

Input Schema

Schema Changelog

TDQS

Other Tools