user_shell_choices
Get a list of available login shells on the system. Useful when creating or updating a user to know which shells are valid.
This record as markdown: /tools/spranab-truenas-mcp/user-shell-choices.md
What user_shell_choices does on Truenas
AI agents call user_shell_choices to retrieve information from Truenas without modifying anything. It is typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
Why user_shell_choices is rated Low
This tool queries system information (available shells) to inform subsequent operations. It retrieves data without side effects, making it a Read operation. The severity is low because knowing valid shell choices poses minimal security risk on its own; it is informational only.
From the tool's definition Tool name 'user_shell_choices' and description states 'Get a list of available login shells on the system' — a pure retrieval operation with no modification, deletion, or execution capabilities.
Attacks that exploit this kind of access
The rule that runs user_shell_choices safely
PolicyLayer is an MCP gateway: it sits between your AI agents and Truenas, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For user_shell_choices, this is the rule to start with:
user_shell_choices is read-only, so it stays allowed. Everything else on the server is denied unless you say otherwise.
The button opens the PolicyLayer dashboard: create your workspace, connect Truenas, apply this rule, and every user_shell_choices call is checked against it from then on.
Questions about user_shell_choices
Get a list of available login shells on the system. Useful when creating or updating a user to know which shells are valid. It is categorised as a Read tool in the Truenas MCP Server, which means it retrieves data without modifying state.
Register the Truenas MCP server in PolicyLayer and add a rule for user_shell_choices: 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 Truenas. Nothing to install.
user_shell_choices 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 user_shell_choices 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 user_shell_choices. 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.
user_shell_choices is provided by the Truenas MCP server (spranab/truenas-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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