AI agents use patch_send_as to create or update resources in Gmail MCP — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Gmail MCP environment.
This tool modifies existing email alias settings rather than creating new ones or deleting them. The blast radius is medium: an attacker could alter how emails appear to be sent from (changing sender identity), potentially enabling spoofing or impersonation attacks, but cannot directly delete data or move money. Classified as Write because it reverses the configuration change via another patch operation.
From the tool's definition Tool name 'patch_send_as' and description 'Patches the specified send-as alias' indicate modification of email alias configuration. 'Patch' is a standard REST verb for partial updates to existing resources.
Documented attack patterns abuse exactly the kind of access patch_send_as gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Gmail MCP, and nothing reaches the server without passing your rules. This is the rule we recommend for patch_send_as:
{
"version": "1",
"default": "deny",
"tools": {
"patch_send_as": {
"limits": [
{
"counter": "patch_send_as_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}patch_send_as 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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Patches the specified send-as alias. It is categorised as a Write tool in the Gmail MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Gmail MCP server in PolicyLayer and add a rule for patch_send_as: 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 Gmail MCP. Nothing to install.
patch_send_as 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 patch_send_as 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 patch_send_as. 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.
patch_send_as is provided by the Gmail MCP server (shinzo-labs/gmail-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 65 Gmail MCP tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
65 Gmail MCP tools catalogued and risk-classified — across an index of 42,500+ MCP servers.