How to Build an AI Agent for Microsoft 365 and Slack

The workflow problem

Mergers, acquisitions, and enterprise sprawl create a painfully common scenario: half the organization uses Microsoft Teams while the other half uses Slack. The acquiring company mandated Teams three years ago, but the product and engineering teams never left Slack. Or the sales team uses Teams because it integrates with Outlook and SharePoint, while engineering lives in Slack because it integrates with GitHub and their deployment pipeline.

The result is organizational information silos at the messaging layer. An engineering decision made in Slack never reaches the project manager in Teams. A client requirement documented in a Teams meeting recording is invisible to the developer assigned to build it. People join both platforms but only actively monitor one, so messages in the other go unanswered for hours or days.

File sharing compounds the problem. A product spec created in SharePoint and shared in Teams is inaccessible to the engineer in Slack without a separate SharePoint login. Meeting notes from Teams meetings are stored in OneDrive; Slack users never see them. The same document gets copied, edited independently on both platforms, and the versions diverge.

Calendar conflicts are another pain point. A Teams user schedules a meeting that conflicts with an event only visible in Slack’s Google Calendar integration. Nobody discovers the conflict until both meetings are underway with half the expected attendees.

Why an AI agent, not just automation

A simple message forwarder between Teams and Slack is technically feasible but practically unusable. It would duplicate every message across both platforms, doubling notification noise and making threading impossible. Users in both systems would see every message twice. It does not scale.

An AI agent understands the organizational structure and routes information intelligently. It knows that the #frontend-team Slack channel corresponds to the “Frontend Engineering” Teams channel. It understands that a message from the VP of Product in Teams about a deadline change is high-priority for the engineering leads in Slack, but a casual Teams conversation about the office holiday party is not.

The agent also handles the format translation that hybrid collaboration demands. A Teams message with an @mention of a Teams user gets translated for Slack with the corresponding Slack user mention if they exist on both platforms. A Slack message with a code snippet gets formatted correctly for Teams, which uses a different markdown syntax. File attachments shared in one platform are made accessible in the other with proper links.

Most importantly, the agent preserves conversational context across platforms. When a Slack thread references a decision made in Teams last week, the agent can surface that Teams conversation so the Slack participants have full context without leaving their platform.

How it works with ACP

ACP connects to Microsoft 365 via Microsoft Graph API (OAuth 2.0 with Azure AD) and to Slack via the Slack Platform with OAuth 2.0. The agent bridges communication while respecting both platforms’ native behaviors.

Microsoft 365 tools available: Read and send Teams channel messages. Read and reply to Teams threads. List Teams channels and members. Access SharePoint files and folders. Read OneDrive documents. Read and create Outlook calendar events. Search across Teams messages. Read meeting transcripts and recordings metadata.

Slack tools available: Read and post channel messages. Create and reply to threads. List channels and members. Search message history. Upload and share files. Read and set user status. Access Slack Connect channels for external collaboration.

The agent maintains a channel mapping table and a user identity map across both platforms. This allows it to route messages to the correct destination and translate user references accurately.

Here is a realistic cross-platform scenario:

Microsoft Teams, “Product Leadership” channel, 2:15 PM: Lisa Chen: “We’re moving the v4.0 launch from March 15 to April 1. The compliance review is taking longer than expected. @David please update the engineering timeline accordingly.”

Agent action – posts to Slack #engineering-leads, 2:15 PM: “Timeline Update from Product Leadership (Teams) Lisa Chen announced that the v4.0 launch is moving from March 15 to April 1. Reason: compliance review is taking longer than expected. David (engineering) has been asked to update the engineering timeline.

Source: Teams ‘Product Leadership’ channel. [View original in Teams]”

Slack #engineering-leads, 2:22 PM: @david.r: “Acknowledged. I’ll update the sprint plan. This actually helps – we can squeeze in the performance fixes from the backlog. I’ll share an updated timeline by EOD.”

Agent action – replies in Teams “Product Leadership” thread, 2:23 PM: “Update from Engineering (via Slack): David acknowledged the timeline shift and notes it allows time for backlog performance fixes. Updated sprint plan coming by EOD.”

The agent did not forward every message from both channels. It identified a cross-team-relevant decision and routed it with the appropriate context and formatting for each audience.

Governance and security

Bridging Microsoft 365 and Slack involves connecting two platforms that each contain highly sensitive organizational data. Access control must be meticulous.

Microsoft Graph API permissions: The agent requests ChannelMessage.Read.All and ChannelMessage.Send for Teams messaging, Files.Read.All for SharePoint/OneDrive file access, and Calendars.Read for scheduling. These are application-level permissions granted through Azure AD admin consent. The agent does not request Mail.Read (Outlook email) or User.ReadWrite.All (user management). Private Teams chats are excluded unless explicitly configured.

Slack OAuth scopes: The agent requests channels:read, channels:history, chat:write, and files:read. It does not access private channels or direct messages by default. Slack Enterprise Grid organizations can restrict the agent to specific workspaces.

Cross-platform data policy: The agent enforces configurable routing rules about what information can cross the platform boundary. Messages in Teams channels tagged as “Confidential” (using Microsoft sensitivity labels) are never forwarded to Slack. Slack channels with restricted membership can be excluded from the bridge. Administrators define the routing policy, and the agent enforces it.

Identity mapping security: The cross-platform user map is stored within ACP’s secure configuration and is not accessible to end users. It is maintained by administrators to ensure accurate routing without exposing personal information across platforms.

Audit trail: Every cross-platform message route is logged with the source platform, channel, user, destination platform, channel, timestamp, and content hash. Compliance teams can audit cross-platform information flow for regulatory purposes, particularly important in financial services and healthcare where information barriers must be maintained.

Example use cases

• Decision broadcast: When a senior leader posts a decision in Teams, the agent identifies it as cross-platform-relevant and posts a summary in the corresponding Slack channel, ensuring engineering teams are informed without requiring them to monitor Teams.

• Incident bridge: During a production incident, the agent creates a linked thread in both Teams (for leadership visibility) and Slack (for engineering coordination), synchronizing key updates so both audiences stay informed in real time.

• File accessibility: When a SharePoint document is shared in Teams, the agent posts a direct link in the relevant Slack channel with a preview summary, so Slack users can access the document without navigating SharePoint independently.

• Meeting notes distribution: After a Teams meeting, the agent reads the meeting transcript summary, identifies action items, and posts them to the relevant Slack channels with assignee mentions translated to Slack usernames.

• Calendar conflict detection: The agent monitors Outlook calendars and Slack-integrated Google Calendars to flag scheduling conflicts for users who operate on both platforms, sending a Slack DM before double-bookings solidify.

Getting started

Unify your hybrid collaboration environment in minutes:

1. Sign up at cloud.agenticcontrolplane.com and create a workspace for your organization.
2. Connect your tools by authorizing Microsoft 365 through Azure AD and installing the Slack app through the Data Sources page. Map your Teams channels to their Slack counterparts and configure identity mappings.
3. Describe your agent in plain English: “Route important decisions and timeline changes from the Teams Product Leadership channel to Slack #engineering-leads, and sync engineering status updates back.” The agent will present its routing rules for your review.