Adds symbols to a watchlist across supported brokers.
AI agents use unified_add_to_watchlist to create or update resources in Open Stocks MCP — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Open Stocks MCP environment.
This tool modifies user watchlist data (a form of personal preference/metadata), which is a reversible Write operation. It does not execute trades (Execute category), delete data (Destructive), move money (Financial), or trigger external code execution. The severity is low because modifying a watchlist has minimal blast radius—an erroneous addition harms only the user's own preferences and can be easily undone.
From the tool's definition The tool name and description indicate it "Adds symbols to a watchlist" - a write operation that creates or modifies watchlist data reversibly. Watchlists are metadata/preferences that track user interest in securities without executing trades or moving money.
Documented attack patterns abuse exactly the kind of access unified_add_to_watchlist gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Open Stocks MCP, and nothing reaches the server without passing your rules. This is the rule we recommend for unified_add_to_watchlist:
{
"version": "1",
"default": "deny",
"tools": {
"unified_add_to_watchlist": {
"limits": [
{
"counter": "unified_add_to_watchlist_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}unified_add_to_watchlist stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
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Adds symbols to a watchlist across supported brokers. It is categorised as a Write tool in the Open Stocks MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Open Stocks MCP server in PolicyLayer and add a rule for unified_add_to_watchlist: 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 Open Stocks MCP. Nothing to install.
unified_add_to_watchlist is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the unified_add_to_watchlist 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 unified_add_to_watchlist. 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.
unified_add_to_watchlist is provided by the Open Stocks MCP server (open-agent-tools/open-stocks-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Open Stocks MCP, 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.
152 Open Stocks MCP tools catalogued and risk-classified — across an index of 43,000+ MCP servers.