Composite daily-refresh driver. Calls fetch_bars \u2192 fetch_chain \u2192 fetch_quotes \u2192 compute_vix_context for a caller-supplied universe, then returns coverage report. Intended for scheduled jobs (cron, /schedule skill, etc.) that populate the cache nightly with yesterday
AI agents call refresh_market_data to retrieve information from Tradeblocks without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
Even though refresh_market_data only reads data, uncontrolled read access leaks sensitive information and racks up API costs — an agent caught in a retry loop can make thousands of calls a minute without anyone noticing.
Attacks that exploit this kind of access
Composite daily-refresh driver. Calls fetch_bars \u2192 fetch_chain \u2192 fetch_quotes \u2192 compute_vix_context for a caller-supplied universe, then returns coverage report. Intended for scheduled jobs (cron, /schedule skill, etc.) that populate the cache nightly with yesterday. It is categorised as a Read tool in the Tradeblocks MCP Server, which means it retrieves data without modifying state.
Register the Tradeblocks MCP server in PolicyLayer and add a rule for refresh_market_data: 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 Tradeblocks. Nothing to install.
refresh_market_data 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 refresh_market_data 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 refresh_market_data. 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.
refresh_market_data is provided by the Tradeblocks MCP server (tradeblocks-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.