AI agents call get_filter to retrieve information from Gmail MCP without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool queries and retrieves an existing email filter configuration from Gmail. It performs no data modification, deletion, or external operations. It is purely informational and read-only in nature. The low severity reflects minimal blast radius if misused—an AI agent could only view filter configurations, which may expose some settings but cannot alter email behavior or cause data loss.
From the tool's definition Tool name 'get_filter' and description 'Gets a filter' indicate a retrieval operation with no modification or side effects.
Documented attack patterns abuse exactly the kind of access get_filter 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 get_filter:
{
"version": "1",
"default": "deny",
"tools": {
"get_filter": {}
}
}get_filter is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Gets a filter. It is categorised as a Read tool in the Gmail MCP MCP Server, which means it retrieves data without modifying state.
Register the Gmail MCP server in PolicyLayer and add a rule for get_filter: 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.
get_filter is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the get_filter 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 get_filter. 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.
get_filter 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.
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65 Gmail MCP tools catalogued and risk-classified — across an index of 42,500+ MCP servers.