Mailrith Email Marketing

Send a broadcast now

broadcasts_send

Destructive

Immediately creates durable preparation for a broadcast draft or scheduled send. Mailrith calculates the exact Subscriber total and checks provider readiness in the background before delivery. A 202 response means the durable send was accepted, not that provider delivery is complete. Reuse the same idempotency key if the response is lost. Effect: external-email. Retry with the same idempotency_key. Permissions: live_actions:write, broadcasts:write. API reference: https://mailrith.com/developers/api-reference.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "broadcast_id": "<broadcast_id>"
    },
    "name": "broadcasts_send"
  }
}

Input Schema

Name	Required	Description
`body`	No	The exact JSON request body defined by the Mailrith public API contract.
`broadcast_id`	Yes	The broadcast identifier.
`idempotency_key`	No	Optional idempotency key to retry the request safely. It must not exceed 256 UTF-8 bytes.

Output Schema

Name	Required	Description
`error`	No
`response`	No
`request_id`	Yes	The stable correlation ID for this MCP tool invocation.
`operation_id`	Yes	The stable Mailrith public API operation ID.

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedNov 2, 2026

changedOutput schema / $defs / Broadcast / properties / reply_to_email / anyOf

Previous value: -[
-  {
-    "type": "string"
-  },
-  {
-    "type": "null"
-  }
-]New value: +[
+  {
+    "description": "An override for this email's Reply-To. Null uses the sender's current Reply-To when the email is sent.",
+    "type": "string"
+  },
+  {
+    "type": "null"
+  }
+]

Changed5 schema fields changedSep 3, 2026

changedInput schema / properties / idempotency_key / description

Previous value: -"Optional idempotency key to make retries safe."New value: +"Optional idempotency key to retry the request safely. It must not exceed 256 UTF-8 bytes."

addedInput schema / properties / idempotency_key / maxLength
```
Added value: +256
```

changedOutput schema / $defs / BroadcastEmailDocument / description

Previous value: -"A structured email document. The root node must use type `doc` and contain supported block nodes."New value: +"A structured email document. The root node must use type `doc` and contain supported block nodes. For Subscriber personalization in email subjects and body text nodes, use Mailrith bracket tokens such as [Subscriber_Name, fallback=\"friend\"] or [Subscriber_Email, fallback=\"\"]. Before using a custom field, call custom_fields_list or custom_fields_get and copy its personalization_token exactly. Do not use Handlebars-style variables such as {{ subscriber.name }}; Mailrith sends them as literal text."

changedOutput schema / $defs / BroadcastEmailDocument / example / content

Previous value: -[
-  {
-    "content": [
-      {
-        "text": "Hello from Mailrith.",
-        "type": "text"
-      }
-    ],
-    "type": "paragraph"
-  }
-]New value: +[
+  {
+    "content": [
+      {
+        "text": "Hello [Subscriber_Name, fallback=\"friend\"].",
+        "type": "text"
+      }
+    ],
+    "type": "paragraph"
+  }
+]

changedOutput schema / $defs / BroadcastEmailDocument / examples

Previous value: -[
-  {
-    "content": [
-      {
-        "content": [
-          {
-            "text": "Hello from Mailrith.",
-            "type": "text"
-          }
-        ],
-        "type": "paragraph"
-      }
-    ],
-    "type": "doc"
-  }
-]New value: +[
+  {
+    "content": [
+      {
+        "content": [
+          {
+            "text": "Hello [Subscriber_Name, fallback=\"friend\"].",
+            "type": "text"
+          }
+        ],
+        "type": "paragraph"
+      }
+    ],
+    "type": "doc"
+  }
+]

Changed5 schema fields changedSep 3, 2026

changedInput schema / properties / idempotency_key / description

Previous value: -"Optional idempotency key to retry the request safely. It must not exceed 256 UTF-8 bytes."New value: +"Optional idempotency key to make retries safe."

removedInput schema / properties / idempotency_key / maxLength
```
Removed value: -256
```

changedOutput schema / $defs / BroadcastEmailDocument / description

Previous value: -"A structured email document. The root node must use type `doc` and contain supported block nodes. For Subscriber personalization in email subjects and body text nodes, use Mailrith bracket tokens such as [Subscriber_Name, fallback=\"friend\"] or [Subscriber_Email, fallback=\"\"]. Before using a custom field, call custom_fields_list or custom_fields_get and copy its personalization_token exactly. Do not use Handlebars-style variables such as {{ subscriber.name }}; Mailrith sends them as literal text."New value: +"A structured email document. The root node must use type `doc` and contain supported block nodes."

changedOutput schema / $defs / BroadcastEmailDocument / example / content

Previous value: -[
-  {
-    "content": [
-      {
-        "text": "Hello [Subscriber_Name, fallback=\"friend\"].",
-        "type": "text"
-      }
-    ],
-    "type": "paragraph"
-  }
-]New value: +[
+  {
+    "content": [
+      {
+        "text": "Hello from Mailrith.",
+        "type": "text"
+      }
+    ],
+    "type": "paragraph"
+  }
+]

changedOutput schema / $defs / BroadcastEmailDocument / examples

Previous value: -[
-  {
-    "content": [
-      {
-        "content": [
-          {
-            "text": "Hello [Subscriber_Name, fallback=\"friend\"].",
-            "type": "text"
-          }
-        ],
-        "type": "paragraph"
-      }
-    ],
-    "type": "doc"
-  }
-]New value: +[
+  {
+    "content": [
+      {
+        "content": [
+          {
+            "text": "Hello from Mailrith.",
+            "type": "text"
+          }
+        ],
+        "type": "paragraph"
+      }
+    ],
+    "type": "doc"
+  }
+]

Changed2 schema fields changedAug 21, 2026

changedInput schema / properties / idempotency_key / description

Previous value: -"Optional idempotency key to make retries safe."New value: +"Optional idempotency key to retry the request safely. It must not exceed 256 UTF-8 bytes."

addedInput schema / properties / idempotency_key / maxLength
```
Added value: +256
```

Changed3 schema fields changedAug 17, 2026

changedOutput schema / $defs / BroadcastEmailDocument / description

Previous value: -"A structured email document. The root node must use type `doc` and contain supported block nodes."New value: +"A structured email document. The root node must use type `doc` and contain supported block nodes. For Subscriber personalization in email subjects and body text nodes, use Mailrith bracket tokens such as [Subscriber_Name, fallback=\"friend\"] or [Subscriber_Email, fallback=\"\"]. Before using a custom field, call custom_fields_list or custom_fields_get and copy its personalization_token exactly. Do not use Handlebars-style variables such as {{ subscriber.name }}; Mailrith sends them as literal text."

changedOutput schema / $defs / BroadcastEmailDocument / example / content

Previous value: -[
-  {
-    "content": [
-      {
-        "text": "Hello from Mailrith.",
-        "type": "text"
-      }
-    ],
-    "type": "paragraph"
-  }
-]New value: +[
+  {
+    "content": [
+      {
+        "text": "Hello [Subscriber_Name, fallback=\"friend\"].",
+        "type": "text"
+      }
+    ],
+    "type": "paragraph"
+  }
+]

changedOutput schema / $defs / BroadcastEmailDocument / examples

Previous value: -[
-  {
-    "content": [
-      {
-        "content": [
-          {
-            "text": "Hello from Mailrith.",
-            "type": "text"
-          }
-        ],
-        "type": "paragraph"
-      }
-    ],
-    "type": "doc"
-  }
-]New value: +[
+  {
+    "content": [
+      {
+        "content": [
+          {
+            "text": "Hello [Subscriber_Name, fallback=\"friend\"].",
+            "type": "text"
+          }
+        ],
+        "type": "paragraph"
+      }
+    ],
+    "type": "doc"
+  }
+]

First observedJul 30, 2026

TDQS

A3.6/5.0

Behavior4/5

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

The description adds substantial context beyond annotations: background subscriber-total calculation, provider readiness checks, 202 response meaning, idempotency-key retry behavior, required permissions, and external-email effect. It does not fully explain irreversibility or delivery failure handling, but annotations already provide destructive/open-world hints.

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

Conciseness3/5

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

The core send semantics and 202 caveat are front-loaded, but the description repeats idempotency retry guidance twice and uses some jargon. Most sentences are useful, but redundancy and wording reduce efficiency.

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

Completeness4/5

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

Given the annotations, full schema coverage, and output schema, the description is largely complete for an agent to invoke this tool correctly. The main remaining gap is workflow guidance around preflight/send-test and cancellation, which is more usage-guideline territory than raw completeness.

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 100%, so broadcast_id and preflight_proof are already well documented in the schema. The description adds useful idempotency-key retry semantics, but it does not add meaning for the other parameters.

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?

The description and title make clear this sends a broadcast immediately rather than scheduling it, and the external-email effect is stated explicitly. However, the phrase 'durable preparation' is jargon-heavy and the description does not directly name siblings like broadcasts_schedule or broadcasts_send_test for contrast.

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 word 'Immediately' implies when to use this instead of scheduling, and retry guidance is included. But there is no explicit when-not guidance, no recommendation to preflight or send-test first, and no comparison to broadcasts_cancel or broadcasts_get_send_progress.

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

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Tool call template

Input Schema

Output Schema

Schema Changelog

TDQS

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