Retrieves the contents of a file from the server, with optional base64 encoding. Primarily used to access log files, screenshots, and other assets generated during browser automation. Set encode_base64=True for binary files like images. Has a configurable size limit (default 10MB) to prevent exce...
AI agents call fetch_file to retrieve information from Nova Act without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool performs a straightforward read operation that queries and retrieves file data without side effects. It includes safeguards (size limits, optional encoding) to prevent misuse but does not create, modify, delete, or execute anything.
From the tool's definition Tool description explicitly states 'Retrieves the contents of a file from the server' with no mention of modification, deletion, or execution capabilities. Primary use cases are 'log files, screenshots, and other assets' which are read-only operations.
Documented attack patterns abuse exactly the kind of access fetch_file gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Nova Act, and nothing reaches the server without passing your rules. This is the rule we recommend for fetch_file:
{
"version": "1",
"default": "deny",
"tools": {
"fetch_file": {}
}
}fetch_file is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Retrieves the contents of a file from the server, with optional base64 encoding. Primarily used to access log files, screenshots, and other assets generated during browser automation. Set encode_base64=True for binary files like images. Has a configurable size limit (default 10MB) to prevent excessive token usage with large files. It is categorised as a Read tool in the Nova Act MCP Server, which means it retrieves data without modifying state.
Register the Nova Act MCP server in PolicyLayer and add a rule for fetch_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 Nova Act. Nothing to install.
fetch_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 fetch_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 fetch_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.
fetch_file is provided by the Nova Act MCP server (madtank/nova-act-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Nova Act, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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9 Nova Act tools catalogued and risk-classified — across an index of 43,000+ MCP servers.