Send a text message via Messenger to a user. Requires the recipient PSID (Page-Scoped ID). Note: 24-hour messaging window applies — can only respond within 24h of the user's last message.
Part of the Facebook Pages server.
Free to start. No card required.
AI agents use fb_send_message to create or modify resources in Facebook Pages. 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 fb_send_message 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 Facebook Pages.
Write tools can modify data. A rate limit prevents runaway bulk operations from AI agents.
{
"version": "1",
"default": "deny",
"tools": {
"fb_send_message": {
"limits": [
{
"counter": "fb_send_message_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}See the full Facebook Pages policy for all 28 tools.
These attack patterns abuse exactly the kind of access fb_send_message 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.
Send a text message via Messenger to a user. Requires the recipient PSID (Page-Scoped ID). Note: 24-hour messaging window applies — can only respond within 24h of the user's last message.. It is categorised as a Write tool in the Facebook Pages MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Facebook Pages MCP server in PolicyLayer and add a rule for fb_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 Facebook Pages. Nothing to install.
fb_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 fb_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 fb_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.
fb_send_message is provided by the Facebook Pages MCP server (node2flow/facebook-pages). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 28 Facebook Pages tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
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