Add an address to a TIP-403 policy blacklist (block the address).
AI agents use add_to_blacklist to create or update resources in Tempo — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Tempo environment.
This tool modifies blockchain state by adding an address to a blacklist, preventing that address from transacting. While it has significant business impact (blocking user access), it is reversible—addresses can be removed from the blacklist. It does not permanently delete data or irreversibly destroy assets, so it does not qualify as Destructive.
From the tool's definition Tool description states 'Add an address to a TIP-403 policy blacklist (block the address)' — this creates or modifies a blacklist data structure by adding an entry, which is a reversible write operation (the address can be removed later).
Documented attack patterns abuse exactly the kind of access add_to_blacklist gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Tempo, and nothing reaches the server without passing your rules. This is the rule we recommend for add_to_blacklist:
{
"version": "1",
"default": "deny",
"tools": {
"add_to_blacklist": {
"limits": [
{
"counter": "add_to_blacklist_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}add_to_blacklist 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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Add an address to a TIP-403 policy blacklist (block the address). It is categorised as a Write tool in the Tempo MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Tempo MCP server in PolicyLayer and add a rule for add_to_blacklist: 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 Tempo. Nothing to install.
add_to_blacklist 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 add_to_blacklist 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 add_to_blacklist. 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.
add_to_blacklist is provided by the Tempo MCP server (arome3/tempo-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Tempo, 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.
61 Tempo tools catalogued and risk-classified — across an index of 43,000+ MCP servers.