plot_time_series · VayuChat MCP: Risk & Policy

WHAT IT DOES

What plot_time_series does on VayuChat MCP

AI agents invoke plot_time_series to trigger actions in VayuChat MCP. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

WHY IT NEEDS A POLICY

Why plot_time_series needs a policy

Generating a plot on this server involves executing Python code (matplotlib/pandas) to produce a visualization. While the primary output is a chart (read-like in intent), the mechanism is code execution with potential side effects such as writing files to disk. The server explicitly states it executes Python code, so this falls under Execute rather than Read.

From the tool's definition 'Create a time series plot' combined with server description noting 'execute Python code with pandas and numpy' and 'generate matplotlib visualizations'

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

plot_time_series Rate-limited

plot_time_series stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "plot_time_series": {
      "limits": [
        {
          "counter": "plot_time_series_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-LIMIT THIS TOOL →

Instant setup, no code required.

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

FAQ

Questions about plot_time_series

What does the plot_time_series tool do? +

Create a time series plot. It is categorised as a Execute tool in the VayuChat MCP MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on plot_time_series? +

Register the VayuChat MCP server in PolicyLayer and add a rule for plot_time_series: 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 VayuChat MCP. Nothing to install.

What risk level is plot_time_series? +

plot_time_series is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit plot_time_series? +

Yes. Add a rate_limit block to the plot_time_series 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 plot_time_series completely? +

Set action: deny in the PolicyLayer policy for plot_time_series. 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 plot_time_series? +

plot_time_series is provided by the VayuChat MCP server (nipunbatra/vayuchat-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.