Update the spending limit for an access key on a specific token.
AI agents use update_spending_limit 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 an existing spending limit (a reversible Write operation) rather than executing a payment or irreversibly deleting data. However, severity is high because misconfiguring spending limits on a blockchain stablecoin payment system could enable unauthorized transactions up to the new limit, creating significant financial exposure.
From the tool's definition Tool description states 'Update the spending limit' — this modifies access control parameters for a token, which is a reversible change to system configuration.
Documented attack patterns abuse exactly the kind of access update_spending_limit 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 update_spending_limit:
{
"version": "1",
"default": "deny",
"tools": {
"update_spending_limit": {
"limits": [
{
"counter": "update_spending_limit_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}update_spending_limit 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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Update the spending limit for an access key on a specific token. 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 update_spending_limit: 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.
update_spending_limit 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 update_spending_limit 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 update_spending_limit. 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.
update_spending_limit 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.