List available languages. Returns: Information about available languages
AI agents call list_languages to retrieve information from Tree Sitter without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool performs a read-only query operation that returns metadata about supported languages. It has no side effects, does not execute code, does not modify data, and does not create any irreversible changes. The low severity reflects minimal blast radius if misused—an agent could at worst spam requests or learn which languages are supported, posing no risk to code or system integrity.
From the tool's definition Tool name 'list_languages' and description 'List available languages' indicates a retrieval operation that returns information about available languages without modifying any state.
Documented attack patterns abuse exactly the kind of access list_languages gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Tree Sitter, and nothing reaches the server without passing your rules. This is the rule we recommend for list_languages:
{
"version": "1",
"default": "deny",
"tools": {
"list_languages": {}
}
}list_languages is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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List available languages. Returns: Information about available languages. It is categorised as a Read tool in the Tree Sitter MCP Server, which means it retrieves data without modifying state.
Register the Tree Sitter MCP server in PolicyLayer and add a rule for list_languages: 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 Tree Sitter. Nothing to install.
list_languages 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 list_languages 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 list_languages. 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.
list_languages is provided by the Tree Sitter MCP server (wrale/mcp-server-tree-sitter). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 26 Tree Sitter tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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26 Tree Sitter tools catalogued and risk-classified — across an index of 42,500+ MCP servers.