Watch a single market by slug via WebSocket and return the first change event. Times out if no change occurs. Requires the market slug, not the market app ID.
AI agents call stream_market to retrieve information from Alpha Arcade without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
stream_market retrieves real-time market data via WebSocket streaming. It has no side effects on the market or user positions. While it is part of a trading platform server, this specific tool only reads/observes market state changes. It does not create orders, execute trades, modify data, or move funds. The 'watch' and 'stream' semantics indicate passive data consumption.
From the tool's definition Tool description states 'Watch a single market by slug via WebSocket and return the first change event.' This is a passive observation/fetch operation that retrieves live market data without modifying, deleting, or executing transactions.
Documented attack patterns abuse exactly the kind of access stream_market gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Alpha Arcade, and nothing reaches the server without passing your rules. This is the rule we recommend for stream_market:
{
"version": "1",
"default": "deny",
"tools": {
"stream_market": {}
}
}stream_market is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Watch a single market by slug via WebSocket and return the first change event. Times out if no change occurs. Requires the market slug, not the market app ID. It is categorised as a Read tool in the Alpha Arcade MCP Server, which means it retrieves data without modifying state.
Register the Alpha Arcade MCP server in PolicyLayer and add a rule for stream_market: 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 Alpha Arcade. Nothing to install.
stream_market 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 stream_market 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 stream_market. 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.
stream_market is provided by the Alpha Arcade MCP server (phara23/alpha-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Alpha Arcade, 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.
20 Alpha Arcade tools catalogued and risk-classified — across an index of 43,000+ MCP servers.