update_session · Pelaris MCP: Risk & Policy

WHAT IT DOES

What update_session does on Pelaris

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

WHY IT NEEDS A POLICY

Why update_session needs a policy

The tool modifies existing fitness session data (title, focus, duration, status, RPE, feedback, exercises, coach notes) but does not delete or irreversibly destroy data. This is a classic Write operation: creates or modifies data reversibly. Severity is medium because misuse could corrupt a user's fitness tracking history, but impacts are limited to a single user's workout logs and can be corrected by updating again.

From the tool's definition Tool description states it 'Update[s] an existing session with corrected or additional data — title, focus, duration, status, RPE, feedback, exercises, or coach notes.' This is reversible modification of workout session records.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

update_session Rate-limited

update_session 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": {
    "update_session": {
      "limits": [
        {
          "counter": "update_session_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 Pelaris, so you can run agents against it safely.

FAQ

Questions about update_session

What does the update_session tool do? +

Update an existing session with corrected or additional data — title, focus, duration, status, RPE, feedback, exercises, or coach notes. It is categorised as a Write tool in the Pelaris MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on update_session? +

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

What risk level is update_session? +

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

Can I rate-limit update_session? +

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

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

update_session is provided by the Pelaris MCP server (thedonk/pelaris-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.