Slack Code Mode MCP

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Execute Slack API code

execute

Run JavaScript in a network-isolated V8 isolate to chain Slack Web API calls and app lookups, returning values; credentials are brokered by the host.

Instructions

Run JavaScript inside a network-isolated celld V8 isolate. Prefer app.* for lookups, DMs, posts, threads, links, files, and canvases; slack exposes the allowlisted Web API. Return a value to get it back; console output is included.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "code": "<code>"
    },
    "name": "execute"
  }
}

Input Schema

Name	Required	Description	Default
`code`	Yes	JavaScript body. Use `return` for the value you want back.
`timeout_ms`	No	Execution limit in milliseconds (default 30000).

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.4.0Oct 20, 2026

TDQS

B3.4/5.0

Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description carries the burden. It discloses key traits: network isolation, an allowlisted Web API, return-value semantics, and console output inclusion. However, it omits authentication requirements, error handling, and rate limits, so it is substantial but not complete.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Three sentences, front-loaded with the core action, then usage guidance, then return behavior. No fluff, and each sentence serves a purpose.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness3/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a code-execution tool with no output schema and no annotations, the description covers the environment and API surface well. Yet it leaves out auth requirements and error/rate-limit behavior, which are important for correct invocation.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so the baseline is 3. The description adds only a small note about returning a value and console output, which is already partly in the schema's `code` description; it adds little beyond structured fields.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb+resource: run JavaScript in a network-isolated V8 isolate for Slack API code. It names the accessible namespaces (`app.*` and `slack`), making the tool's scope clear. However, it does not explicitly differentiate from the sibling `search` tool, so a 4 rather than 5.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives internal guidance on which namespace to use for different actions, but never states when to choose this tool over the `search` sibling or when not to use it. No conditions, prerequisites, or alternatives are mentioned for tool selection.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

Deploy Server

Other Tools

executeB
searchA