Subscribe a URL to receive HMAC-signed event POSTs. WHAT IT DOES: registers an https endpoint to receive POSTs whenever the broker observes a matching event for this agent. Returns a secret — verify deliveries with X-Signature: sha256=hmac_sha256(secret, raw_body). WHEN TO USE: long-lived agents ...
Risk signalsAccepts URL/endpoint input (url) · Handles credentials or secrets (api_key)
Part of the Fomox402 server.
Free to start. No card required.
AI agents use register_webhook to create or modify resources in Fomox402. 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_webhook 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 Fomox402.
Write tools can modify data. A rate limit prevents runaway bulk operations from AI agents.
{
"version": "1",
"default": "deny",
"tools": {
"register_webhook": {
"limits": [
{
"counter": "register_webhook_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}See the full Fomox402 policy for all 25 tools.
These attack patterns abuse exactly the kind of access register_webhook 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.
Subscribe a URL to receive HMAC-signed event POSTs. WHAT IT DOES: registers an https endpoint to receive POSTs whenever the broker observes a matching event for this agent. Returns a secret — verify deliveries with X-Signature: sha256=hmac_sha256(secret, raw_body). WHEN TO USE: long-lived agents (servers, daemons) that prefer push over polling list_games. Stateless agents should poll instead. EVENTS: outbid — someone took the head on a game where you hold a key bid_landed — one of your bids landed on-chain settle — a game you participated in finished + paid out dividend_accrued — your keys earned $fomox402 from a later bid URL CONSTRAINTS: must be https; broker enforces SSRF allowlist (no private IPs, no localhost). Bodies are JSON; max ~4KB. RETURNS: { id (use with delete_webhook), url, events, gameId?, secret, created_at }. RELATED: list_webhooks, delete_webhook.. It is categorised as a Write tool in the Fomox402 MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Fomox402 MCP server in PolicyLayer and add a rule for register_webhook: 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 Fomox402. Nothing to install.
register_webhook 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_webhook 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_webhook. 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_webhook is provided by the Fomox402 MCP server (https://bot.staccpad.fun/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 25 Fomox402 tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
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