Purpose: Set the TipTap JSON content of a broadcast, enabling it to be edited visually in the Resend dashboard editor. Automatically connects and disconnects from the editor. Can also update metadata (subject, preview text, name) in the same call. This is the recommended way to set email content....
AI agents use compose-broadcast to create or update resources in Email Sending MCP — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Email Sending MCP environment.
This tool creates/modifies broadcast email content and metadata in the Resend dashboard. It writes data reversibly (content can be edited again later), and does not send the email itself. Severity is medium because misconfigured broadcast content could affect many recipients if later sent, but the tool itself only sets/updates content without triggering delivery.
From the tool's definition Set the TipTap JSON content of a broadcast... Can also update metadata (subject, preview text, name) in the same call
Documented attack patterns abuse exactly the kind of access compose-broadcast gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Email Sending MCP, and nothing reaches the server without passing your rules. This is the rule we recommend for compose-broadcast:
{
"version": "1",
"default": "deny",
"tools": {
"compose-broadcast": {
"limits": [
{
"counter": "compose-broadcast_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}compose-broadcast stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
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Purpose: Set the TipTap JSON content of a broadcast, enabling it to be edited visually in the Resend dashboard editor. Automatically connects and disconnects from the editor. Can also update metadata (subject, preview text, name) in the same call. This is the recommended way to set email content. Content set via compose-broadcast can be visually edited by the user in the dashboard. Use this for newsletters and any broadcast where the user may want to refine the content. Workflow: get-tiptap-json-content (with include_schema: true) → compose-broadcast When to use: - After create-broadcast, to set the email body - When the user wants to write, edit, or style email content - When the user wants to collaborate on the email in the dashboard editor Important: Always call get-tiptap-json-content first to retrieve the existing TipTap JSON, then build your changes on top of it. Skipping this will overwrite all existing content. Note: Switching between compose (TipTap) and update (raw HTML) modes is lossy — some content or formatting may be lost. If the broadcast already has HTML content, ask the user before switching to compose mode. It is categorised as a Write tool in the Email Sending MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Email Sending MCP server in PolicyLayer and add a rule for compose-broadcast: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Email Sending MCP. Nothing to install.
compose-broadcast is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the compose-broadcast rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for compose-broadcast. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
compose-broadcast is provided by the Email Sending MCP server (resend/resend-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 77 Email Sending MCP tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
77 Email Sending MCP tools catalogued and risk-classified — across an index of 42,500+ MCP servers.