AI agents call extract_fields to retrieve information from SharkMCP without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool performs data retrieval and querying operations on packet captures—it reads and extracts packet field information without modifying, deleting, or executing anything. The blast radius is minimal: extracted packet data cannot harm systems or trigger external operations. It is a read-only introspection capability, falling squarely into the Read category.
From the tool's definition The tool 'extract_fields' extracts arbitrary fields per packet from PCAP/PCAPNG files. The description states it extracts fields 'per packet' with no mention of modification, deletion, or execution capabilities.
Documented attack patterns abuse exactly the kind of access extract_fields gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and SharkMCP, and nothing reaches the server without passing your rules. This is the rule we recommend for extract_fields:
{
"version": "1",
"default": "deny",
"tools": {
"extract_fields": {}
}
}extract_fields is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Extract arbitrary fields per packet, e.g. It is categorised as a Read tool in the SharkMCP MCP Server, which means it retrieves data without modifying state.
Register the Shark MCP server in PolicyLayer and add a rule for extract_fields: 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 SharkMCP. Nothing to install.
extract_fields 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 extract_fields 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 extract_fields. 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.
extract_fields is provided by the Shark MCP server (weirdmachine64/sharkmcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 30 SharkMCP tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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30 SharkMCP tools catalogued and risk-classified — across an index of 42,500+ MCP servers.