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Update a broadcast

update_broadcast

Destructive

Modify a Kit broadcast's content, subject, schedule, audience filters, or publish status; requires confirm=true for changes that affect delivery or published data.

Instructions

Update 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
`broadcast_id`	Yes	Positive broadcast id.
`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: +{
+  "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`.",
+    "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": {
+            "additionalProperties": false,
+            "properties": {
+              "ids": {
+                "items": {
+                  "type": "integer"
+                },
+                "type": "array"
+              },
+              "type": {
+                "description": "`segment` or `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`",
+                "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`",
+                "type": "string"
+              }
+            },
+            "required": [
+              "type",
+              "ids"
+            ],
+            "type": "object"
+          },
+          "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`."

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`."

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`",
-            "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`",
-            "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`",
-            "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`",
-            "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`",
-            "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`",
-            "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

A3.7/5.0

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 bar is lower, yet the description adds real value: it enumerates what can be affected (delivery, audience membership, published data, irreversible state) and states the confirm=true requirement. It doesn't describe reversibility per-field or auth needs beyond confirm.

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

Conciseness5/5

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

Two compact sentences with zero filler; the impact warning and the confirm prerequisite are front-loaded. Nothing is wasted.

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

Completeness3/5

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

For an 18-param destructive mutation with a rich nested schema and no output schema, the description covers the safety profile adequately but omits return behavior and gives no guidance on the payload vs. individual flags distinction. It's minimally complete but leaves meaningful gaps for a tool this complex.

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

Parameters3/5

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

Schema coverage is 61%, so the schema already documents many params (content, payload, send_at, subscriber_filter, email_address, etc.). The description only surfaces confirm=true, leaving the other 17 params to the schema. Baseline 3 is appropriate for this coverage level with minimal description-side parameter detail.

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

Purpose4/5

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

Clear verb+resource ('Update a broadcast') and it cites the affected domains (delivery, audience membership, published data, irreversible state), which distinguishes it from create_broadcast and delete_broadcast. It stops short of naming those siblings explicitly, so it lands just under a 5.

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?

The description implies when the tool is used (modifying an existing broadcast) but gives no explicit when-to-use vs. when-not-to-use guidance or alternatives. The 'Requires confirm=true' clause is a procedural precondition that helps, but it isn't framed as decision guidance.

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

Deploy Server

Update a broadcast

Instructions

Input Schema

Schema Changelog

TDQS

Other Tools