AI agents use timers_increment to create or update resources in Propresenter — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Propresenter environment.
This tool modifies the state of a timer by incrementing its value. This is a reversible write operation (the timer can be decremented or reset), affecting only presentation timing within ProPresenter 7. The blast radius is low as it only impacts live presentation timer state.
From the tool's definition Increment a specific timer by a duration
Documented attack patterns abuse exactly the kind of access timers_increment gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Propresenter, and nothing reaches the server without passing your rules. This is the rule we recommend for timers_increment:
{
"version": "1",
"default": "deny",
"tools": {
"timers_increment": {
"limits": [
{
"counter": "timers_increment_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}timers_increment 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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Increment a specific timer by a duration. It is categorised as a Write tool in the Propresenter MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Propresenter MCP server in PolicyLayer and add a rule for timers_increment: 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 Propresenter. Nothing to install.
timers_increment 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 timers_increment 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 timers_increment. 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.
timers_increment is provided by the Propresenter MCP server (@alxpark/propresenter-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Propresenter, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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