AI agents use fast_apply to create or update resources in Relace MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Relace MCP Server environment.
An AI agent can call fast_apply faster than any human can review — one bad instruction and it creates or modifies resources in Relace MCP Server by the hundred, each call as confident as the last.
Documented attack patterns abuse exactly the kind of access fast_apply gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Relace MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for fast_apply:
{
"version": "1",
"default": "deny",
"tools": {
"fast_apply": {
"limits": [
{
"counter": "fast_apply_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}fast_apply 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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fast_apply. It is categorised as a Write tool in the Relace MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Relace MCP Server MCP server in PolicyLayer and add a rule for fast_apply: 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 Relace MCP Server. Nothing to install.
fast_apply 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 fast_apply 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 fast_apply. 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.
fast_apply is provided by the Relace MCP Server MCP server (possible055/relace-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 8 Relace MCP Server tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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8 Relace MCP Server tools catalogued and risk-classified — across an index of 42,500+ MCP servers.