set_chat_message_reaction · Teams MCP: Risk & Policy

WHAT IT DOES

What set_chat_message_reaction does on Teams

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

WHY IT NEEDS A POLICY

Why set_chat_message_reaction needs a policy

Adding a reaction modifies the state of a message by appending reaction metadata, which is a Write operation. It is reversible (reactions can be removed) and has no destructive effects. Severity is medium because an AI agent could spam reactions across many messages, degrading user experience and consuming rate limits, but the action itself is non-destructive and low-impact to system integrity.

From the tool's definition The tool 'Add a reaction to a message' performs a reversible modification operation. Reactions are metadata attachments to messages that can be added or removed without permanently altering message content or deleting data.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

set_chat_message_reaction Rate-limited

set_chat_message_reaction 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": {
    "set_chat_message_reaction": {
      "limits": [
        {
          "counter": "set_chat_message_reaction_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 Teams, so you can run agents against it safely.

FAQ

Questions about set_chat_message_reaction

What does the set_chat_message_reaction tool do? +

Add a reaction to a message in a chat conversation. Supports Unicode emoji characters and named reactions (like, angry, sad, laugh, heart, surprised). It is categorised as a Write tool in the Teams MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on set_chat_message_reaction? +

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

What risk level is set_chat_message_reaction? +

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

Can I rate-limit set_chat_message_reaction? +

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

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

set_chat_message_reaction is provided by the Teams MCP server (@floriscornel/teams-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.