add_to_watchlist · MCP YFinance Stock Server MCP

WHAT IT DOES

What add_to_watchlist does on MCP YFinance Stock Server

AI agents use add_to_watchlist to create or update resources in MCP YFinance Stock Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your MCP YFinance Stock Server environment.

WHY IT NEEDS A POLICY

Why add_to_watchlist needs a policy

This tool modifies user state by adding stocks to a watchlist—a reversible write operation. It does not delete data (not Destructive), execute arbitrary code (not Execute), or involve financial transactions (not Financial). Severity is medium because misuse could spam a watchlist with thousands of entries or pollute user data, but the impact is confined to one user's watchlist and easily reversible.

From the tool's definition Tool name 'add_to_watchlist' indicates creation/modification of user watchlist data. The server description confirms it 'manage[s] watchlists' as a core feature.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

add_to_watchlist Rate-limited

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.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "add_to_watchlist": {
      "limits": [
        {
          "counter": "add_to_watchlist_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches MCP YFinance Stock Server, so you can run agents against it safely.

FAQ

Questions about add_to_watchlist

What does the add_to_watchlist tool do? +

add_to_watchlist. It is categorised as a Write tool in the MCP YFinance Stock Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on add_to_watchlist? +

Register the MCP YFinance Stock Server MCP server in PolicyLayer and add a rule for 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 MCP YFinance Stock Server. Nothing to install.

What risk level is add_to_watchlist? +

add_to_watchlist is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit add_to_watchlist? +

Yes. Add a rate_limit block to the 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.

How do I block add_to_watchlist completely? +

Set action: deny in the PolicyLayer policy for 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.

What MCP server provides add_to_watchlist? +

add_to_watchlist is provided by the MCP YFinance Stock Server MCP server (sauniket/mcp-yfinance-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.