slack-skills-plugin is a plugin that connects coding agents to Slack through a Slack MCP server and provides Slack-focused skills for users and developers. It is used with Claude Code, Cursor, Codex, and other coding agents to work with Slack and build Slack applications. The catalogue entries are the plugin's included skills, commands, MCP server, instructions, and settings.
Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add skills/slackapi/slack-skills-plugin/test-slack-appnpx skills add slackapi/slack-skills-plugin --skill test-slack-appgit clone --depth 1 https://github.com/slackapi/slack-skills-pluginWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/slackapi/slack-skills-plugin/test-slack-app)<a href="https://agentmods.dev/skills/slackapi/slack-skills-plugin/test-slack-app"><img src="https://agentmods.dev/badge/skills/slackapi/slack-skills-plugin/test-slack-app.svg" alt="Measured on agentmods" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00107 | $0.02106 |
| Opus 5 | $0.00053 | $0.01053 |
| Sonnet 5 | $0.00021 | $0.00421 |
| Haiku 4.5 | $0.00011 | $0.00211 |
Grade A, and why
test-slack-app scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 6d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 111 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Test Slack App
Help a developer confirm that a Slack app they already built actually works. This is the last step of the build loop, after the slack:create-slack-app skill scaffolds an app and the slack:slack-cli skill runs it.
The approach is simple and safe:
- Run the app in a developer sandbox: a free, throwaway Slack org for building and testing, never a workspace with real coworkers in it.
- Read the app's source to learn what it actually listens for.
- Hand the developer concrete steps to perform in Slack, then help them confirm the app responds.
This is guided manual checking, not an automated test suite: you drive the setup and tell the developer what to type or click, and they confirm what they see. It works best for apps managed by the Slack CLI; there is a best-effort path for plain Bolt apps in Step 2.
Step 1: Set Up a Safe Place to Test
1a. Detect the Slack CLI
Use the slack:slack-cli skill (Step 1: Detect the Slack CLI) to check whether the public Slack CLI is installed and resolve its command name. The fingerprint check, alias fallback, and install instructions all live there; do not duplicate them here. Refer to the resolved command as SLACK_CMD throughout. If the CLI is not installed, guide the developer through that same step to install it, since running the app needs it.
1b. Make sure there is a developer sandbox to test in
Testing belongs in a developer sandbox, never a workspace with real coworkers in it.
- Explain it from the live docs, not from here. Use the
slack:slack-docsskill to fetch and summarize https://docs.slack.dev/tools/developer-sandboxes.md, so the recommendation always reflects the current docs rather than a copy that drifts out of date. Tell the developer that Slack recommends a sandbox for building and testing apps. - Find the current target. Run
SLACK_CMD auth listfor the authenticated workspaces and their team IDs, and, from the project directory,SLACK_CMD app listfor the apps already installed and their IDs. - Confirm it is a sandbox. The CLI cannot tell a sandbox apart from a workspace with real users, so ask the developer to confirm the target is a developer sandbox. If there is no sandbox yet, set one up with the
slack:create-slack-appskill (Step 3: Set Up a Developer Sandbox), which owns thesandbox list/sandbox createflow and the Developer Program links. Creating a sandbox happens in the browser, so have the developer come back here once the sandbox exists and they have logged into it.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 6d ago First seen · 111 lines · 107 tokens per session scan A 7b10aac8c954
test-slack-app is a skill published in the GitHub repository slackapi/slack-skills-plugin (120 stars, last pushed today), licensed MIT. It adds 107 tokens to every session and 2,106 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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