feat(workflows): add mcp tool to make an email template transactional

products/messaging/backend/presentation/views/message_templates.py

@@ -791,7 +791,8 @@ def _require_transactional_email_flag(self) -> None:
         summary="Make a template transactional",
         description=(
             "Make this template sendable over the transactional email API. This creates the workflow that sends it, "
-            "with its own metrics, run history and versions. Calling it again on a transactional template changes "
+            "with its own metrics, run history and versions. This can't be undone: the template stays transactional. "
+            "Transactional sends ignore marketing opt-outs. Calling it again on a transactional template changes "
             "nothing."
         ),
         parameters=[TEMPLATE_ID_PARAMETER],

products/workflows/frontend/TemplateLibrary/MakeTransactionalPrompt.tsx

@@ -34,6 +34,7 @@ export function MakeTransactionalPrompt(props: MessageTemplateSceneLogicProps):
                     Your edits save as a draft. Publishing updates the live email, and each publish keeps a version.
                 </li>
                 <li>Transactional emails ignore marketing opt-outs, so don't use them for marketing.</li>
+                <li>You can't undo this. The template stays transactional.</li>
             </ul>
             <div>
                 <LemonButton

products/workflows/mcp/email_templates.yaml

@@ -77,6 +77,36 @@ tools:
                 - content
                 - created_by
                 - draft_content
+    workflows-make-email-template-transactional:
+        operation: messaging_templates_make_transactional_create
+        enabled: true
+        scopes:
+            - hog_flow:write
+        annotations:
+            readOnly: false
+            destructive: true
+            idempotent: true
+        enrich_url: '{id}'
+        title: Make email template transactional
+        description: >
+            Make an email template sendable from code with one API call, for emails a person triggers such as password
+            resets, receipts and sign-in codes. This is one-way: the template can't be made non-transactional again.
+            Transactional sends ignore marketing opt-outs, so never use this for marketing email. The template needs a
+            subject and a body, and the project needs a verified email sender (pass from_integration_id to pick one,
+            otherwise the project's default sender is used). Requires human typed confirmation. The response has
+            transactional_hog_flow_id, the workflow that sends the email. Share the template's _posthogUrl so the user
+            can review and publish it.
+        feature_flag: workflows-transactional-email-api
+        response:
+            exclude:
+                - content
+                - draft_content
+                - created_by
+        confirmed_action:
+            message: >
+                About to make email template '{id}' transactional. This can't be undone, and its sends will ignore
+                marketing opt-outs. Reply 'confirm' to proceed.
+            action_label: make email template transactional
     workflows-patch-email-template:
         operation: messaging_templates_design_partial_update
         enabled: true

services/mcp/schema/tool-definitions-all.json

@@ -17192,6 +17192,37 @@
             "readOnlyHint": true
         }
     },
+    "workflows-make-email-template-transactional-execute": {
+        "description": "Step 2 of 2 for make email template transactional. Verifies the confirmation_hash from -prepare and the literal \"confirm\" string typed by the user, then performs the action. ONLY call this after the user has explicitly typed \"confirm\" in chat. Original action: Make an email template sendable from code with one API call, for emails a person triggers such as password resets, receipts and sign-in codes. This is one-way: the template can't be made non-transactional again. Transactional sends ignore marketing opt-outs, so never use this for marketing email. The template needs a subject and a body, and the project needs a verified email sender (pass from_integration_id to pick one, otherwise the project's default sender is used). Requires human typed confirmation. The response has transactional_hog_flow_id, the workflow that sends the email. Share the template's _posthogUrl so the user can review and publish it.",
+        "category": "Workflows",
+        "feature": "workflows",
+        "summary": "Make email template transactional (execute)",
+        "title": "Make email template transactional (execute)",
+        "required_scopes": ["hog_flow:write"],
+        "api_operations": ["POST /api/projects/{project_id}/messaging_templates/{id}/make_transactional/"],
+        "annotations": {
+            "destructiveHint": true,
+            "idempotentHint": true,
+            "openWorldHint": true,
+            "readOnlyHint": false
+        },
+        "feature_flag": "workflows-transactional-email-api"
+    },
+    "workflows-make-email-template-transactional-prepare": {
+        "description": "Step 1 of 2 for make email template transactional. Validates the arguments and returns a signed confirmation_hash plus a message to surface to the user. The user must reply with the literal word \"confirm\" before you call the matching -execute tool with the hash. Original action: Make an email template sendable from code with one API call, for emails a person triggers such as password resets, receipts and sign-in codes. This is one-way: the template can't be made non-transactional again. Transactional sends ignore marketing opt-outs, so never use this for marketing email. The template needs a subject and a body, and the project needs a verified email sender (pass from_integration_id to pick one, otherwise the project's default sender is used). Requires human typed confirmation. The response has transactional_hog_flow_id, the workflow that sends the email. Share the template's _posthogUrl so the user can review and publish it.",
+        "category": "Workflows",
+        "feature": "workflows",
+        "summary": "Make email template transactional (prepare)",
+        "title": "Make email template transactional (prepare)",
+        "required_scopes": ["hog_flow:write"],
+        "annotations": {
+            "destructiveHint": false,
+            "idempotentHint": true,
+            "openWorldHint": true,
+            "readOnlyHint": true
+        },
+        "feature_flag": "workflows-transactional-email-api"
+    },
     "workflows-patch-action-email": {
         "description": "Surgically edit the email inside one function_email step - the fastest path for copy tweaks and design changes on a workflow email. Use operations (the same design ops as workflows-patch-email-template, addressing blocks by id from the step's config.inputs.email.value.design) to edit the design, and email_patch to change subject, preheader, text, or recipients. After design ops the HTML is re-rendered server-side, so the sent email always matches the design. Edits apply atomically: an invalid batch changes nothing. On an active workflow, edits stage a draft (composing with any staged graph edits) and nothing reaches real people until workflows-publish. The full updated workflow is returned. Prefer this over workflows-patch-graph update_action for email content - it's smaller to send and keeps design and HTML in sync. For library templates use workflows-patch-email-template instead.",
         "category": "Workflows",