// MCP TOOL REFERENCE

SLACK_REGISTERS_A_NEW_CALL_WITH_PARTICIPANTS

DEPRECATED: Registers a new call in Slack using `calls.add` for third-party call integration. Use `start_call` instead.

Part of the Slack MCP server. Enforce policies on this tool with Intercept, the open-source MCP proxy.

@modelcontextprotocol/server-slack Execute Risk 3/5

// WHEN AI AGENTS USE THIS TOOL

AI agents invoke SLACK_REGISTERS_A_NEW_CALL_WITH_PARTICIPANTS to trigger processes or run actions in Slack. Execute operations can have side effects beyond the immediate call -- triggering builds, sending notifications, or starting workflows. Rate limits and argument validation are essential to prevent runaway execution.

// WHY ENFORCE A POLICY ON SLACK_REGISTERS_A_NEW_CALL_WITH_PARTICIPANTS

SLACK_REGISTERS_A_NEW_CALL_WITH_PARTICIPANTS can trigger processes with real-world consequences. An uncontrolled agent might start dozens of builds, send mass notifications, or kick off expensive compute jobs. Intercept enforces rate limits and validates arguments to keep execution within safe bounds.

// RECOMMENDED POLICY

Execute tools trigger processes. Rate-limit and validate arguments to prevent unintended side effects.

slack.yaml

tools:
  SLACK_REGISTERS_A_NEW_CALL_WITH_PARTICIPANTS:
    rules:
      - action: allow
        rate_limit:
          max: 10
          window: 60
        validate:
          required_args: true

See the full Slack policy for all 143 tools.

// DETAILS

Tool Name SLACK_REGISTERS_A_NEW_CALL_WITH_PARTICIPANTS

Category Execute

MCP Server Slack MCP Server

Risk Level High

// MORE SLACK TOOLS

Destructive SLACK_CLEAR_STATUS Destructive SLACK_CUSTOMIZE_URL_UNFURL Destructive SLACK_DELETE_A_COMMENT_ON_A_FILE Destructive SLACK_DELETE_A_FILE_BY_ID Destructive SLACK_DELETE_A_PUBLIC_OR_PRIVATE_CHANNEL Destructive SLACK_DELETE_A_SCHEDULED_MESSAGE_IN_A_CHAT Destructive SLACK_DELETE_A_SLACK_REMINDER Destructive SLACK_DELETE_CANVAS

View all 143 tools →

// WHAT CAN GO WRONG

Agents calling execute-class tools like SLACK_REGISTERS_A_NEW_CALL_WITH_PARTICIPANTS have been implicated in these attack patterns. Read the full case and prevention policy for each:

Browse the full MCP Attack Database →

// OTHER EXECUTE TOOLS ACROSS MCP SERVERS

Other tools in the Execute risk category across the catalogue. The same policy patterns (rate-limit, validate) apply to each.

Agent Passport System — Cryptographic Identity for AI Agents commerce_preflight Agent Passport System — Cryptographic Identity for AI Agents execute_with_context Agent Passport System — Cryptographic Identity for AI Agents gateway_execute_approval Agent Passport System — Cryptographic Identity for AI Agents governance_360 Agent Passport System — Cryptographic Identity for AI Agents parse_governance_block_html AgentClear — API Marketplace for AI Agents call_service

// IN CONTEXT OF HIGH RISK

SLACK_REGISTERS_A_NEW_CALL_WITH_PARTICIPANTS is one of the high-risk operations in Slack. For the full severity-focused view — only the high-risk tools with their recommended policies — see the breakdown for this server, or browse all high-risk tools across every MCP server.

// RELATED READING

// FAQ

What does the SLACK_REGISTERS_A_NEW_CALL_WITH_PARTICIPANTS tool do? +

DEPRECATED: Registers a new call in Slack using `calls.add` for third-party call integration. Use `start_call` instead.. It is categorised as a Execute tool in the Slack MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on SLACK_REGISTERS_A_NEW_CALL_WITH_PARTICIPANTS? +

Add a rule in your Intercept YAML policy under the tools section for SLACK_REGISTERS_A_NEW_CALL_WITH_PARTICIPANTS. You can allow, deny, rate-limit, or validate arguments. Then run Intercept as a proxy in front of the Slack MCP server.

What risk level is SLACK_REGISTERS_A_NEW_CALL_WITH_PARTICIPANTS? +

SLACK_REGISTERS_A_NEW_CALL_WITH_PARTICIPANTS is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit SLACK_REGISTERS_A_NEW_CALL_WITH_PARTICIPANTS? +

Yes. Add a rate_limit block to the SLACK_REGISTERS_A_NEW_CALL_WITH_PARTICIPANTS rule in your Intercept 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 SLACK_REGISTERS_A_NEW_CALL_WITH_PARTICIPANTS completely? +

Set action: deny in the Intercept policy for SLACK_REGISTERS_A_NEW_CALL_WITH_PARTICIPANTS. 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 SLACK_REGISTERS_A_NEW_CALL_WITH_PARTICIPANTS? +

SLACK_REGISTERS_A_NEW_CALL_WITH_PARTICIPANTS is provided by the Slack MCP server (@modelcontextprotocol/server-slack). Intercept sits as a proxy in front of this server to enforce policies before tool calls reach the server.

SLACK_REGISTERS_A_NEW_CALL_WITH_PARTICIPANTS

Enforce policies on Slack