Lint a file at a specific path against Vale style rules. Returns issues found with their locations and severity. If Vale is not installed, returns error with installation guidance.
AI agents call check_file to retrieve information from Vale MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves and analyzes data from a file to report style and grammar issues. It has no side effects on the file system or data—it only reads the file and returns diagnostic information. This is a classic Read operation (analogous to 'query' or 'get' operations).
From the tool's definition Tool performs linting/analysis of a file ('check_file') and 'Returns issues found' without modifying the file.
Documented attack patterns abuse exactly the kind of access check_file gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Vale MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for check_file:
{
"version": "1",
"default": "deny",
"tools": {
"check_file": {}
}
}check_file is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Lint a file at a specific path against Vale style rules. Returns issues found with their locations and severity. If Vale is not installed, returns error with installation guidance. It is categorised as a Read tool in the Vale MCP Server MCP Server, which means it retrieves data without modifying state.
Register the Vale MCP Server MCP server in PolicyLayer and add a rule for check_file: 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 Vale MCP Server. Nothing to install.
check_file 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 check_file 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 check_file. 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.
check_file is provided by the Vale MCP Server MCP server (theletterf/vale-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Vale MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
3 Vale MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.