message-mark

// WHEN AGENTS USE THIS TOOL

AI agents use message-mark to create or modify resources in Gmail. Write operations carry medium risk because an autonomous agent could trigger bulk unintended modifications. Rate limits prevent a single agent session from making hundreds of changes in rapid succession. Argument validation ensures the agent passes expected values.

Without a policy, an AI agent could call message-mark repeatedly, creating or modifying resources faster than any human could review. PolicyLayer's rate limiting ensures write operations happen at a controlled pace, and argument validation catches malformed or unexpected inputs before they reach Gmail.

// RECOMMENDED POLICY

Write tools can modify data. A rate limit prevents runaway bulk operations from AI agents.

{
  "version": "1",
  "default": "deny",
  "tools": {
    "message-mark": {
      "limits": [
        {
          "counter": "message-mark_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

See the full Gmail policy for all 7 tools.

// MORE GMAIL TOOLS

// WHAT CAN GO WRONG

These attack patterns abuse exactly the kind of access message-mark gives an agent. Each links to the full case and the policy that stops it:

• Data exfiltration via tool chaining
• Prompt Injection via Tool Results
• Privilege escalation via admin-only tools

Browse the full MCP Attack Database →

// OTHER WRITE TOOLS

Other write tools across the catalogue. The same approach applies to each: rate-limit and validate the arguments.

// RELATED READING

• Rate Limiting MCP Tool Calls: A Practical Guide
• MCP Security: Why Prompt Guardrails Aren't Enough
• The Case for Deterministic AI Agent Policies
• Why AI Agents Need a Control Plane

// FAQ