Preview the ACL rules that would apply to a specific user or IP address if a proposed policy were applied.
Single-target operation
Part of the Tailscale MCP server. Enforce policies on this tool with Intercept, the open-source MCP proxy.
AI agents call tailscale_preview_acl to retrieve information from Tailscale 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 tailscale_preview_acl 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.
tools:
tailscale_preview_acl:
rules:
- action: allowSee the full Tailscale policy for all 89 tools.
Agents calling read-class tools like tailscale_preview_acl have been implicated in these attack patterns. Read the full case and prevention policy for each:
Other tools in the Read risk category across the catalogue. The same policy patterns (rate-limit, allow) apply to each.
Preview the ACL rules that would apply to a specific user or IP address if a proposed policy were applied.. It is categorised as a Read tool in the Tailscale MCP Server, which means it retrieves data without modifying state.
Add a rule in your Intercept YAML policy under the tools section for tailscale_preview_acl. You can allow, deny, rate-limit, or validate arguments. Then run Intercept as a proxy in front of the Tailscale MCP server.
tailscale_preview_acl 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 tailscale_preview_acl rule in your Intercept 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 Intercept policy for tailscale_preview_acl. 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.
tailscale_preview_acl is provided by the Tailscale MCP server (@yawlabs/tailscale-mcp). Intercept sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic policy on every MCP tool call. Per-identity grants. Full audit log.