Create a new segment in Resend. A segment is a group of contacts that can be used to target specific broadcasts.
AI agents use create-segment 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 a new segment (a data structure for organizing contacts) in Resend. This is a reversible write operation—segments can be created and modified without permanently destroying data or executing arbitrary code. While it could be misused to create segments for targeting in unwanted broadcasts, the core action is data creation rather than destructive deletion, financial transaction, or code execution.
From the tool's definition Tool description states 'Create a new segment' and 'A segment is a group of contacts that can be used to target specific broadcasts.' The verb 'create' and purpose of creating a new organizational grouping indicates data creation/modification.
Documented attack patterns abuse exactly the kind of access create-segment 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 create-segment:
{
"version": "1",
"default": "deny",
"tools": {
"create-segment": {
"limits": [
{
"counter": "create-segment_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}create-segment 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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Create a new segment in Resend. A segment is a group of contacts that can be used to target specific broadcasts. 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 create-segment: 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.
create-segment 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 create-segment 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 create-segment. 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.
create-segment 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.