When you're expecting a fax back — bank confirmation, court filing, signed document — open a 24h receive window at our shared number +1 320 299 1523. Matched by caller ID (last 10 digits of the sender), delivered to your email as soon as it arrives. Optional OCR add-on (+200 sats) returns a searc...
Risk signalsAccepts URL/endpoint input (callback_url)
Part of the Sats4AI - Bitcoin-Powered AI Tools server.
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AI agents use receive_fax to create or modify resources in Sats4AI - Bitcoin-Powered AI Tools. 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 receive_fax 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 Sats4AI - Bitcoin-Powered AI Tools.
Write tools can modify data. A rate limit prevents runaway bulk operations from AI agents.
{
"version": "1",
"default": "deny",
"tools": {
"receive_fax": {
"limits": [
{
"counter": "receive_fax_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}See the full Sats4AI - Bitcoin-Powered AI Tools policy for all 49 tools.
These attack patterns abuse exactly the kind of access receive_fax 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.
When you're expecting a fax back — bank confirmation, court filing, signed document — open a 24h receive window at our shared number +1 320 299 1523. Matched by caller ID (last 10 digits of the sender), delivered to your email as soon as it arrives. Optional OCR add-on (+200 sats) returns a searchable text file alongside the PDF — useful for feeding the content to an agent or archiving. Optional callback_url POSTs an HMAC-signed webhook on delivery so your agent doesn't have to poll. No refund if no fax arrives within the window (prevents subscription squatting). If OCR fails, an LNURL-withdraw for 200 sats is included in the delivery email for partial refund. Pay with Bitcoin Lightning — no dedicated fax number rental, no monthly subscription, no account.. It is categorised as a Write tool in the Sats4AI - Bitcoin-Powered AI Tools MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Sats4AI - Bitcoin-Powered AI Tools MCP server in PolicyLayer and add a rule for receive_fax: 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 Sats4AI - Bitcoin-Powered AI Tools. Nothing to install.
receive_fax 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 receive_fax 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 receive_fax. 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.
receive_fax is provided by the Sats4AI - Bitcoin-Powered AI Tools MCP server (cnghockey/sats4ai-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 49 Sats4AI - Bitcoin-Powered AI Tools tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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