calls_add

A write tool on the Slack MCP server.

SERVERSlack SOURCEkarbassi/slack-mcp

Medium RISK CLASS

Category Write

Parameters 00 required

Recommended Rate-limitedsee the rule below

Registry record Grade F, identity unverified Pull the record →

This record as markdown: /tools/karbassi-slack-mcp/calls-add.md

WHAT IT DOES

What calls_add does on Slack

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

RISK

Why calls_add is rated Medium

The name 'calls_add' follows Slack API naming conventions where 'calls.add' registers a new external call in Slack. 'Add' implies creation/write operation. However, with no description, confidence is reduced. Given the server context (Slack MCP with full access), this likely creates a call record, which is a reversible write operation.

From the tool's definition Tool name 'calls_add' suggests creating/adding a call resource in Slack. Description is empty and uninformative.

Attacks that exploit this kind of access

RECOMMENDED RULE

The rule that runs calls_add safely

PolicyLayer is an MCP gateway: it sits between your AI agents and Slack, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For calls_add, this is the rule to start with:

calls_add Rate-limited

calls_add 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": {
    "calls_add": {
      "limits": [
        {
          "counter": "calls_add_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL → Instant setup, no code required.

The button opens the PolicyLayer dashboard: create your workspace, connect Slack, apply this rule, and every calls_add call is checked against it from then on.

FAQ

Questions about calls_add

What does the calls_add tool do? +

calls_add is a write tool on the Slack MCP server. It is categorised as a Write tool in the Slack MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on calls_add? +

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

What risk level is calls_add? +

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

Can I rate-limit calls_add? +

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

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

calls_add is provided by the Slack MCP server (karbassi/slack-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

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