What is slack-mcp-server CLAUDE.md?

Instructions for building and configuring a Slack server that lets coding agents interact with Slack. Slack is a workplace messaging service; this version also documents optional tools for saved messages and a developer architecture guide.

Use it to install the server for Claude Code, configure browser-session authentication, build it in Go, run it over standard input and output, and optionally enable saved-message tools.

It explains the setup details, authentication tokens, build command, and environment variables needed to run the server, including its fork-specific options.

How lazallen/slack-mcp-server configures Claude Code

Reuse

Borrowing it

Nothing to install: this file belongs to lazallen/slack-mcp-server. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/lazallen/slack-mcp-server/master/CLAUDE.md

Clone the repo

git clone --depth 1 https://github.com/lazallen/slack-mcp-server

Made for: Claude Code.

Wrote 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.

README.md

[![agentmods](https://agentmods.dev/badge/instructions/lazallen/slack-mcp-server/claude-md.svg)](https://agentmods.dev/instructions/lazallen/slack-mcp-server/claude-md)

Your own site

<a href="https://agentmods.dev/instructions/lazallen/slack-mcp-server/claude-md"><img src="https://agentmods.dev/badge/instructions/lazallen/slack-mcp-server/claude-md.svg" alt="Measured on agentmods" height="20"></a>

Per session 969 This file is loaded in full into every session.

When invoked 969 The same file — it is already loaded in full.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin original No closer match found in the catalogue.

Token cost

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	$0.00969	$0.00969
Opus 5	$0.00485	$0.00485
Sonnet 5	$0.00194	$0.00194
Haiku 4.5	$0.00097	$0.00097

Measured 8d ago against content hash 9fc3c0a98d44, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

slack-mcp-server CLAUDE.md 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 8d 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.

CLAUDE.md · 98 lines

How it starts

The opening of the file, as written. The whole thing — 98 lines — stays where its author put it; the contents beside it link to each section on GitHub.

slack-mcp-server — CLAUDE.md

Fork of korotovsky/slack-mcp-server.

What this fork adds

saved_list — lists Slack "Save for Later" items (via undocumented saved.list Webclient API)
saved_complete — marks a saved item as complete (via undocumented saved.update Webclient API)
docs/04-architecture.md — comprehensive developer architecture guide

Both saved tools use browser-session tokens (xoxc/xoxd) only and are opt-in via env vars:

SLACK_MCP_SAVED_LIST_TOOL=true
SLACK_MCP_SAVED_COMPLETE_TOOL=true

Install (Claude Code user-level)

make install          # builds and copies to ~/bin/slack-mcp-server

Then configure ~/.claude.json — see instructions.md in the parent repo.

To store/update Keychain tokens (required for wrapper script, includes no-prompt ACL):

./scripts/keychain-setup.sh        # interactive
./scripts/keychain-setup.sh xoxc-... xoxd-...  # non-interactive

Build & run

go build -o build/slack-mcp-server ./cmd/slack-mcp-server
./build/slack-mcp-server --transport stdio

Environment (minimum for xoxc/xoxd auth)

export SLACK_MCP_XOXC_TOKEN=xoxc-...
export SLACK_MCP_XOXD_TOKEN=xoxd-...

Copy .env.dist to .env and fill in values. Never commit .env.

Run tests

go test ./...

Integration tests require SLACK_MCP_XOXP_TOKEN to be set (see pkg/test/util/mcp.go).

Architecture

See docs/04-architecture.md — covers:

Two-layer API (Webclient vs Edge API)
Token types and routing
Startup/cache warm-up
Middleware stack
Step-by-step guide for adding a new tool (Section 6)
How to discover new undocumented Slack endpoints (Section 7 — tape recorder, DevTools, HTTPToolkit)

Adding a new tool (summary)

Add constant + ValidToolNames entry in pkg/server/server.go
Register with s.AddTool(...) and shouldAddTool(...) gating
Create handler in pkg/handler/ following the pattern in existing files
Add method to SlackAPI interface and implement on MCPSlackClient in pkg/provider/api.go
For new undocumented endpoints, use the tape recorder or HTTPToolkit to capture the wire format

Read the full file on GitHub · 98 lines

Changes

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.

8d ago First seen · 98 lines · 969 tokens per session scan A 9fc3c0a98d44

Subscribe to this mod's changes

slack-mcp-server CLAUDE.md is an instructions file published in the GitHub repository lazallen/slack-mcp-server (2 stars, last pushed 4mo ago), licensed MIT. It adds 969 tokens to every session, about $0.0048 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 2026-08-31.

next.js AGENTS.md

AGENTS.md instructions for vercel/next.js, covering next.js development guide, codebase structure, monorepo overview, core package: packages/next and other important packages.

vercel/next.js · 7,296 tokens

codex AGENTS.md

AGENTS.md instructions for openai/codex, covering rust/codex-rs, the codex-core crate, code review rules, crate api surface and model visible context.

openai/codex · 5,153 tokens

vscode buildNext.instructions.md

Working notes and architecture documentation for the new esbuild-based build system in build/next. Use when making changes to the new build pipeline (transpile/bundle commands, NLS plugin, source-map handling, resource copying, or self-hosting watch tasks).

microsoft/vscode · 6,785 tokens

slack-mcp-server: Instructions file for Claude Code