AI agents use gmail_send_message to create or update resources in Sage MCP — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Sage MCP environment.
Sending an email creates a new, persistent communication artifact that is delivered to recipients. While reversible in some cases (delete drafts, recall within Gmail's limited window), the primary effect is to create and transmit data. This is a Write operation rather than Read (which would be fetching emails) or Execute (which would require running arbitrary code).
From the tool's definition Tool name is 'gmail_send_message' and description states 'Send a new email message'. This creates a new piece of data (an email) that is sent to recipients.
Documented attack patterns abuse exactly the kind of access gmail_send_message gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Sage MCP, and nothing reaches the server without passing your rules. This is the rule we recommend for gmail_send_message:
{
"version": "1",
"default": "deny",
"tools": {
"gmail_send_message": {
"limits": [
{
"counter": "gmail_send_message_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}gmail_send_message 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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Send a new email message. It is categorised as a Write tool in the Sage MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Sage MCP server in PolicyLayer and add a rule for gmail_send_message: 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 Sage MCP. Nothing to install.
gmail_send_message 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 gmail_send_message 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 gmail_send_message. 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.
gmail_send_message is provided by the Sage MCP server (sagemcp/sagemcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 359 Sage MCP tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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359 Sage MCP tools catalogued and risk-classified — across an index of 42,500+ MCP servers.