Data catalog — zero cost. Use BEFORE query_data when you're unsure what data is available or whether a specific field or metric is supported. Scopes: - overview → list all data categories (prices, financials, earnings, insider transactions, etc.) + key fields + computed metrics. Good first call. ...
Part of the Mrmarket Ai server.
Free to start. No card required.
AI agents call describe_data to retrieve information from Mrmarket Ai without modifying any data. This is common in research, monitoring, and reporting workflows where the agent needs context before taking action. Because read operations don't change state, they are generally safe to allow without restrictions -- but you may still want rate limits to control API costs.
Even though describe_data only reads data, uncontrolled read access can leak sensitive information or rack up API costs. An agent caught in a retry loop could make thousands of calls per minute. A rate limit gives you a safety net without blocking legitimate use.
Read-only tools are safe to allow by default. No rate limit needed unless you want to control costs.
{
"version": "1",
"default": "deny",
"tools": {
"describe_data": {}
}
}See the full Mrmarket Ai policy for all 8 tools.
These attack patterns abuse exactly the kind of access describe_data gives an agent. Each links to the full case and the policy that stops it:
Other read tools across the catalogue. The same approach applies to each: allow, with a rate cap to control cost.
Data catalog — zero cost. Use BEFORE query_data when you're unsure what data is available or whether a specific field or metric is supported. Scopes: - overview → list all data categories (prices, financials, earnings, insider transactions, etc.) + key fields + computed metrics. Good first call. - category → full field list for one data category. Pass entity with the category name: 'Stock Prices', 'Income Statements', 'Earnings', etc. - computed_metrics → list of pre-defined computed metrics (ROIC, FCF, D/E, ROE, ROA, margins, EPS/revenue growth, stock return, surprise). - search → keyword search across field names, categories, and computed metrics. Pass search_term: 'volatility', 'dividend', 'capex', etc.. It is categorised as a Read tool in the Mrmarket Ai MCP Server, which means it retrieves data without modifying state.
Register the Mrmarket Ai MCP server in PolicyLayer and add a rule for describe_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 Mrmarket Ai. Nothing to install.
describe_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 describe_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 describe_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.
describe_data is provided by the Mrmarket Ai MCP server (https://mcp.mrmarket.ai/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 8 Mrmarket Ai tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
4,600+ MCP servers and 31,000+ tools scanned and risk-classified.