[cost: free (pure CPU, no network) | read-only, no persistence] Take two SIP messages (typically the same request observed at two adjacent hops - e.g. the INVITE leaving FreeSWITCH and the INVITE arriving at Kamailio) and surface a structured per-header diff: added, removed, mutated (with old/new...
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AI agents call diff_sip_messages to retrieve information from Sipflow 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 diff_sip_messages 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": {
"diff_sip_messages": {}
}
}See the full Sipflow policy for all 22 tools.
These attack patterns abuse exactly the kind of access diff_sip_messages 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.
[cost: free (pure CPU, no network) | read-only, no persistence] Take two SIP messages (typically the same request observed at two adjacent hops - e.g. the INVITE leaving FreeSWITCH and the INVITE arriving at Kamailio) and surface a structured per-header diff: added, removed, mutated (with old/new value), duplicated (single header → many), de-duplicated, whitespace-only-change, parameter-reorder (Via params, From tag), and body-changed. SDP bodies on both sides are delegated to compareSdp for codec / DTLS / ICE diffs. Use FIRST when the user has two captures or two log lines that should be carrying the same message and wants to know what an intermediate proxy / SBC / B2BUA changed. Far more reliable than visual inspection. Pair with: parse_sip_message to inspect either side in isolation; lint_sip_request if the diff reveals the downstream side became malformed; search_sip_docs(vendor=<intermediate>) once you know which hop's behavior is the source of the change.. It is categorised as a Read tool in the Sipflow MCP Server, which means it retrieves data without modifying state.
Register the Sipflow MCP server in PolicyLayer and add a rule for diff_sip_messages: 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 Sipflow. Nothing to install.
diff_sip_messages 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 diff_sip_messages 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 diff_sip_messages. 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.
diff_sip_messages is provided by the Sipflow MCP server (https://mcp.sipflow.dev/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 22 Sipflow tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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