Sets the default S/MIME config for the specified send-as alias
AI agents use set_default_smime_info 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 email security configuration (S/MIME settings) for a send-as alias, which is a Write operation—it changes user settings/preferences but does not execute commands, delete data, or move funds.
From the tool's definition Tool name 'set_default_smime_info' and description 'Sets the default S/MIME config for the specified send-as alias' indicate modification of email security configuration settings. S/MIME configuration is a reversible change to user preferences.
Documented attack patterns abuse exactly the kind of access set_default_smime_info 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 set_default_smime_info:
{
"version": "1",
"default": "deny",
"tools": {
"set_default_smime_info": {
"limits": [
{
"counter": "set_default_smime_info_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}set_default_smime_info 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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Sets the default S/MIME config for 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 set_default_smime_info: 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.
set_default_smime_info 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 set_default_smime_info 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 set_default_smime_info. 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.
set_default_smime_info 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.