Set or update the account-level webhook (callback) URL where Jumio POSTs workflow result notifications. Per-transaction callbackUrl overrides this. Validate signatures using the shared HMAC secret configured in the Jumio portal.
AI agents use register_callback_url to create or update resources in Mcp Ap2 — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Mcp Ap2 environment.
This tool modifies account-level configuration (the webhook callback URL) and can affect how notifications are routed. While it doesn't directly move money or delete data, it can redirect sensitive payment or transaction notifications to attacker-controlled endpoints, potentially enabling credential theft or transaction fraud.
From the tool's definition Tool description states 'Set or update the account-level webhook (callback) URL' — this is a modification operation that creates or updates configuration data.
Documented attack patterns abuse exactly the kind of access register_callback_url gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Mcp Ap2, and nothing reaches the server without passing your rules. This is the rule we recommend for register_callback_url:
{
"version": "1",
"default": "deny",
"tools": {
"register_callback_url": {
"limits": [
{
"counter": "register_callback_url_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}register_callback_url stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
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Set or update the account-level webhook (callback) URL where Jumio POSTs workflow result notifications. Per-transaction callbackUrl overrides this. Validate signatures using the shared HMAC secret configured in the Jumio portal. It is categorised as a Write tool in the Mcp Ap2 MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Mcp Ap2 MCP server in PolicyLayer and add a rule for register_callback_url: 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 Mcp Ap2. Nothing to install.
register_callback_url 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_callback_url 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_callback_url. 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_callback_url is provided by the Mcp Ap2 MCP server (@codespar/mcp-ap2). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Mcp Ap2, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
1300 Mcp Ap2 tools catalogued and risk-classified — across an index of 43,000+ MCP servers.