post_comment · Edstem MCP: Risk & Policy

WHAT IT DOES

What post_comment does on Edstem

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

WHY IT NEEDS A POLICY

Why post_comment needs a policy

This tool creates new data (comments/answers) in a course discussion platform in a reversible manner. Users can typically edit or delete their own posts afterward. It is Write rather than Execute because it doesn't run arbitrary code—it specifically posts formatted content.

From the tool's definition Tool description states "Post a comment or answer on a thread", which creates new content. The server description confirms it enables "managing threads, comments, and course activity" and "posting content".

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

post_comment Rate-limited

post_comment 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": {
    "post_comment": {
      "limits": [
        {
          "counter": "post_comment_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 Edstem, so you can run agents against it safely.

FAQ

Questions about post_comment

What does the post_comment tool do? +

Post a comment or answer on a thread. Content can be markdown. It is categorised as a Write tool in the Edstem MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on post_comment? +

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

What risk level is post_comment? +

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

Can I rate-limit post_comment? +

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

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

post_comment is provided by the Edstem MCP server (rob-9/edstem-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.