Detect replay attacks — identical requests sent multiple times in a time window. Uses SHA256 fingerprint of (agent_id + tool_name + args). Default window: 300 seconds (5 min). Returns is_replay=true/false with duplicate count and first/last seen timestamps.
Part of the Agentguard server.
Free to start. No card required.
AI agents call replay_guard_check to retrieve information from Agentguard without modifying any data. This is common in research, monitoring, and reporting workflows where the agent needs context before taking action. Because read operations don't change state, they are generally safe to allow without restrictions -- but you may still want rate limits to control API costs.
Even though replay_guard_check only reads data, uncontrolled read access can leak sensitive information or rack up API costs. An agent caught in a retry loop could make thousands of calls per minute. A rate limit gives you a safety net without blocking legitimate use.
Read-only tools are safe to allow by default. No rate limit needed unless you want to control costs.
{
"version": "1",
"default": "deny",
"tools": {
"replay_guard_check": {}
}
}See the full Agentguard policy for all 24 tools.
These attack patterns abuse exactly the kind of access replay_guard_check gives an agent. Each links to the full case and the policy that stops it:
Other read tools across the catalogue. The same approach applies to each: allow, with a rate cap to control cost.
Detect replay attacks — identical requests sent multiple times in a time window. Uses SHA256 fingerprint of (agent_id + tool_name + args). Default window: 300 seconds (5 min). Returns is_replay=true/false with duplicate count and first/last seen timestamps.. It is categorised as a Read tool in the Agentguard MCP Server, which means it retrieves data without modifying state.
Register the Agentguard MCP server in PolicyLayer and add a rule for replay_guard_check: 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 Agentguard. Nothing to install.
replay_guard_check is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the replay_guard_check 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 replay_guard_check. 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.
replay_guard_check is provided by the Agentguard MCP server (https://feedoracle.io/guard-oracle/mcp/). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 24 Agentguard tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
4,600+ MCP servers and 31,000+ tools scanned and risk-classified.