Slack Integration

Overview

The Slack integration pulls channel messages into PR reviews. When Nectr reviews a PR, it queries the Slack MCP server for messages related to the PR’s topic or linked channels. This helps reviewers understand team discussions and decisions that influenced the code changes. Example: A PR titled “Migrate to Redis Cluster” triggers a search for Slack messages containing “Redis” or “caching”. Nectr includes relevant discussions in the review context.

Status: The Slack integration is partially implemented. The MCP client method exists (get_slack_messages), but it’s not yet called during the review workflow.

How It Works

Slack integration uses the Model Context Protocol (MCP) — Nectr acts as an MCP client and calls a Slack MCP server to fetch messages.

Graceful Degradation

If SLACK_MCP_URL is not set or the Slack MCP server is offline:

Nectr logs an info message: "SLACK_MCP_URL not configured — skipping Slack message fetch"
Returns an empty list []
Review continues without Slack context

Prerequisites

Slack Workspace (free or paid plan)
Slack Bot Token with required scopes (see below)
Slack MCP Server (self-hosted or cloud-deployed)

Setup Guide

1. Create a Slack App

Navigate to Slack API

Go to api.slack.com/apps → Create New App → From scratch

Configure Bot Scopes

Under OAuth & Permissions → Bot Token Scopes, add:

channels:history — Read public channel messages
channels:read — List public channels
search:read — Search messages

Install App to Workspace

Click Install to Workspace and authorize the bot.

Copy Bot Token

Under OAuth & Permissions, copy the Bot User OAuth Token (xoxb-...).

2. Deploy a Slack MCP Server

You need an external MCP server that implements the search_messages tool. This server bridges Slack’s Web API and the MCP protocol.

Docker (Recommended)
Self-Hosted Python
Hosted Service

docker run -d \
  --name slack-mcp-server \
  -e SLACK_BOT_TOKEN=xoxb-... \
  -p 8003:8000 \
  your-org/slack-mcp-server:latest

git clone https://github.com/your-org/slack-mcp-server
cd slack-mcp-server
pip install -r requirements.txt
SLACK_BOT_TOKEN=xoxb-... uvicorn main:app --port 8003

3. Set Environment Variables

Add the following to Nectr’s .env:

.env

# Slack MCP server URL
SLACK_MCP_URL=http://slack-mcp-server:8003

# Optional: Slack bot token for direct notifications (separate from MCP)
SLACK_BOT_TOKEN=xoxb-...
SLACK_SIGNING_SECRET=...

Note: SLACK_BOT_TOKEN in Nectr’s .env is for direct Slack notifications (posting messages to Slack when a review completes). This is separate from the MCP integration, which pulls messages into reviews.For MCP integration, only SLACK_MCP_URL is required. The MCP server handles authentication.

4. Restart Nectr

docker compose restart backend
# or
uvicorn app.main:app --reload

Usage

Automatic Message Fetching (Roadmap)

Status: This feature is planned but not yet implemented. The get_slack_messages method exists in app/mcp/client.py, but it’s not called during the review workflow.

When fully implemented, Nectr will:

Extract keywords from the PR title and description
Call Slack MCP server with search_messages(channel, query)
Include message context in the AI prompt

Example (future):

from app.mcp.client import mcp_client

messages = await mcp_client.get_slack_messages(
    channel="eng-backend",
    query="Redis caching"
)
# Returns: [
#   {"user": "alice", "text": "Let's migrate to Redis Cluster", "ts": "1709985600.123456", "permalink": "..."},
#   {"user": "bob", "text": "Agreed, current setup can't scale", "ts": "1709985700.123456", "permalink": "..."},
# ]

Manual Testing

Test the Slack MCP server directly:

curl -X POST http://slack-mcp-server:8003/ \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "id": 1,
    "method": "tools/call",
    "params": {
      "name": "search_messages",
      "arguments": {"channel": "eng-backend", "query": "Redis"}
    }
  }'

Expected Response:

{
  "result": {
    "content": [
      {
        "type": "text",
        "text": "[{\"user\": \"alice\", \"text\": \"Let's migrate to Redis Cluster\", \"ts\": \"1709985600.123456\"}]"
      }
    ]
  }
}

Implementation Details

MCPClientManager (Placeholder)

File: app/mcp/client.py (not yet implemented) The method signature exists but is not called during reviews:

async def get_slack_messages(self, channel: str, query: str) -> list[dict]:
    """Fetch Slack messages matching a search query.

    Args:
        channel: Slack channel ID or name (e.g. "eng-backend").
        query:   Free-text search query.

    Returns:
        List of message dicts: {user, text, ts, permalink}.
        Empty list if Slack MCP is not configured or the call fails.
    """
    if not settings.SLACK_MCP_URL:
        logger.info(
            "SLACK_MCP_URL not configured — skipping Slack message fetch "
            "(set SLACK_MCP_URL to enable)"
        )
        return []

    return await self.query_mcp_server(
        server_url=settings.SLACK_MCP_URL,
        tool_name="search_messages",
        args={"channel": channel, "query": query},
    )

MCP Request Format

payload = {
    "jsonrpc": "2.0",
    "id": 1,
    "method": "tools/call",
    "params": {
        "name": "search_messages",
        "arguments": {"channel": "eng-backend", "query": "Redis"}
    },
}

response = await client.post(
    f"{settings.SLACK_MCP_URL}/",
    json=payload,
)

Configuration Reference

SLACK_MCP_URL

string

Base URL of the Slack MCP server (e.g., http://slack-mcp-server:8003)

SLACK_BOT_TOKEN

string

Slack bot token for direct notifications (posting messages to Slack).Note: This is separate from the MCP integration. The MCP server handles authentication internally.

SLACK_SIGNING_SECRET

string

Slack signing secret for verifying webhook requests.Note: Used for Slack bot features (commands, interactivity), not MCP integration.

Troubleshooting

No messages returned

Cause: Slack MCP server is not running or SLACK_MCP_URL is incorrect.Fix:

Test the MCP server directly: curl http://slack-mcp-server:8003/
Check logs: docker logs slack-mcp-server
Verify SLACK_MCP_URL is set in Nectr’s .env

Error: HTTP 401 Unauthorized

Cause: SLACK_BOT_TOKEN is missing or invalid in the MCP server.Fix:

Regenerate token at api.slack.com/apps → Your App → OAuth & Permissions
Ensure token is set in the MCP server’s environment

Error: missing_scope

Cause: Slack bot lacks required scopes (channels:history, channels:read, search:read).Fix:

Add scopes at api.slack.com/apps → Your App → OAuth & Permissions → Scopes
Reinstall the app to your workspace

Messages not relevant to PR

Cause: Search query is too broad or channel is wrong.Fix:

Filter messages by date range (last 7 days only)
Use channel-specific queries (e.g., #eng-backend for backend PRs)

Next Steps

MCP Protocol

Understand how MCP connects Nectr with Slack

Linear Integration

Pull linked issues into PR reviews

Environment Variables

Full configuration reference

Overview

Available Integrations

MCP Server

Slack Integration

Overview

How It Works

Graceful Degradation

Prerequisites

Setup Guide

1. Create a Slack App

2. Deploy a Slack MCP Server

3. Set Environment Variables

4. Restart Nectr

Usage

Automatic Message Fetching (Roadmap)

Manual Testing

Implementation Details

MCPClientManager (Placeholder)

MCP Request Format

Configuration Reference

Troubleshooting

Next Steps

MCP Protocol

Linear Integration

Environment Variables

Build docs developers (and LLMs) love

Overview

Available Integrations

MCP Server

​Overview

​How It Works

​Graceful Degradation

​Prerequisites

​Setup Guide

​1. Create a Slack App

​2. Deploy a Slack MCP Server

​3. Set Environment Variables

​4. Restart Nectr

​Usage

​Automatic Message Fetching (Roadmap)

​Manual Testing

​Implementation Details

​MCPClientManager (Placeholder)

​MCP Request Format

​Configuration Reference

​Troubleshooting

​Next Steps

MCP Protocol

Linear Integration

Environment Variables

Build docs developers (and LLMs) love

Overview

How It Works

Graceful Degradation

Prerequisites

Setup Guide

1. Create a Slack App

2. Deploy a Slack MCP Server

3. Set Environment Variables

4. Restart Nectr

Usage

Automatic Message Fetching (Roadmap)

Manual Testing

Implementation Details

MCPClientManager (Placeholder)

MCP Request Format

Configuration Reference

Troubleshooting

Next Steps