Pre-register an expected inbound shipment so it is auto-matched when it arrives at the facility. Optionally specify an action to auto-execute on arrival (e.g. forward immediately, scan on receipt).
Part of the Mailbox server.
Free to start. No card required.
AI agents use register_expected to create or modify resources in Mailbox. 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 register_expected 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 Mailbox.
Write tools can modify data. A rate limit prevents runaway bulk operations from AI agents.
{
"version": "1",
"default": "deny",
"tools": {
"register_expected": {
"limits": [
{
"counter": "register_expected_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}See the full Mailbox policy for all 29 tools.
These attack patterns abuse exactly the kind of access register_expected gives an agent. Each links to the full case and the policy that stops it:
Other write tools across the catalogue. The same approach applies to each: rate-limit and validate the arguments.
Pre-register an expected inbound shipment so it is auto-matched when it arrives at the facility. Optionally specify an action to auto-execute on arrival (e.g. forward immediately, scan on receipt).. It is categorised as a Write tool in the Mailbox MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Mailbox MCP server in PolicyLayer and add a rule for register_expected: 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 Mailbox. Nothing to install.
register_expected 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 register_expected 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 register_expected. 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.
register_expected is provided by the Mailbox MCP server (https://mailbox.bot/api/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 29 Mailbox tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
4,600+ MCP servers and 31,000+ tools scanned and risk-classified.