add_mattermost_reaction · Mattermost MCP Server MCP

WHAT IT DOES

What add_mattermost_reaction does on Mattermost MCP Server

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

WHY IT NEEDS A POLICY

Why add_mattermost_reaction needs a policy

Adding a reaction creates/modifies metadata on an existing message in a reversible manner—reactions can be removed. This is a write operation (creates new data) rather than destructive, execute, or financial. Severity is low because reactions have minimal blast radius: they affect only message decoration and do not alter core message content, user accounts, or channel structure.

From the tool's definition Tool name 'add_mattermost_reaction' indicates creation of a reaction (emoji response) to a message. The description is empty, limiting direct evidence, but the sibling tools include 'post_mattermost_message' (clearly Write) and other message/channel…

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

add_mattermost_reaction Rate-limited

add_mattermost_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": {
    "add_mattermost_reaction": {
      "limits": [
        {
          "counter": "add_mattermost_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 Mattermost MCP Server, so you can run agents against it safely.

FAQ

Questions about add_mattermost_reaction

What does the add_mattermost_reaction tool do? +

add_mattermost_reaction. It is categorised as a Write tool in the Mattermost MCP 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_mattermost_reaction? +

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

What risk level is add_mattermost_reaction? +

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

Can I rate-limit add_mattermost_reaction? +

Yes. Add a rate_limit block to the add_mattermost_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 add_mattermost_reaction completely? +

Set action: deny in the PolicyLayer policy for add_mattermost_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 add_mattermost_reaction? +

add_mattermost_reaction is provided by the Mattermost MCP Server MCP server (vnikhilbuddhavarapu/mattermost-gcp-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.