/teams-app-developer

rest-only-integration-ts

purpose

Raw HTTP integration patterns for Teams and Slack without native SDKs — Bot Framework REST API for Teams, Slack Events API + Web API for Slack. For Java, C#, Go, or any language that lacks an official Bolt or Teams SDK.

rules

1. Use the Bot Framework REST API for Teams when no SDK is available. The REST API is language-agnostic. Authenticate via Azure AD OAuth2 client credentials, then POST activities to the Bot Connector service URL.
2. Use the Slack Events API + Web API for Slack when no Bolt SDK is available. Receive events via HTTP POST webhooks (with signature verification), respond via chat.postMessage and other Web API methods.
3. Verify Slack request signatures manually. Compute HMAC-SHA256 of v0:{timestamp}:{request_body} using your signing secret. Compare against the X-Slack-Signature header. Reject if timestamp is older than 5 minutes.
4. Verify Teams JWT tokens manually. Validate the Authorization: Bearer <token> header against Azure AD's OpenID configuration. Check iss, aud (your app ID), and token expiration. Use your platform's JWT library.
5. Acquire Bot Framework tokens via Azure AD. POST to https://login.microsoftonline.com/{tenantId}/oauth2/v2.0/token with client_id, client_secret, and scope=https://api.botframework.com/.default.
6. Send Teams messages via the Bot Connector API. POST to {serviceUrl}/v3/conversations/{conversationId}/activities with the activity JSON and a Bearer token. The serviceUrl comes from the inbound activity.
7. Send Slack messages via the Web API. POST to https://slack.com/api/chat.postMessage with Authorization: Bearer xoxb-... and a JSON body containing channel, text, and optionally blocks.
8. Acknowledge Slack events within 3 seconds. Return HTTP 200 immediately, then process async. For interactions (actions, commands, shortcuts), return a JSON body or empty 200 to acknowledge.
9. Handle the Slack URL verification challenge. When Slack sends { type: "url_verification", challenge: "..." }, respond with { challenge: "..." } and HTTP 200. This only happens once during setup.
10. Return HTTP 200/201 for Teams webhook POSTs. The Bot Framework expects a 200 response. For invoke activities, return a JSON body with { status: 200, body: ... }.
11. Store the serviceUrl from Teams activities. Each inbound activity includes a serviceUrl that may change. Use it for subsequent API calls to that conversation. Cache per conversation.
12. Use response_url for Slack interaction responses. Actions, commands, and shortcuts include a response_url. POST to it within 30 minutes with { text, response_type } for follow-up messages without needing the Web API.

patterns

Slack signature verification (pseudocode, any language)

function verifySlackSignature(signingSecret, timestamp, body, signature):
    if abs(now() - timestamp) > 300:  // 5 minutes
        return false
    basestring = "v0:" + timestamp + ":" + body
    computed = "v0=" + hmac_sha256(signingSecret, basestring)
    return timingSafeCompare(computed, signature)

// HTTP handler:
timestamp = request.headers["X-Slack-Request-Timestamp"]
signature = request.headers["X-Slack-Signature"]
if not verifySlackSignature(SECRET, timestamp, rawBody, signature):
    return 401

Teams token acquisition (HTTP, any language)

POST https://login.microsoftonline.com/{tenantId}/oauth2/v2.0/token
Content-Type: application/x-www-form-urlencoded

client_id={appId}
&client_secret={appPassword}
&scope=https://api.botframework.com/.default
&grant_type=client_credentials

Response: { "access_token": "eyJ...", "expires_in": 3600 }

Send a Teams message (HTTP, any language)

POST {serviceUrl}/v3/conversations/{conversationId}/activities
Authorization: Bearer {access_token}
Content-Type: application/json

{
  "type": "message",
  "text": "Hello from a REST client!",
  "from": { "id": "{botAppId}", "name": "My Bot" }
}

Send a Slack message (HTTP, any language)

POST https://slack.com/api/chat.postMessage
Authorization: Bearer xoxb-your-token
Content-Type: application/json

{
  "channel": "C123ABC",
  "text": "Hello from a REST client!",
  "blocks": [
    {
      "type": "section",
      "text": { "type": "mrkdwn", "text": "Hello from a REST client!" }
    }
  ]
}

Slack event webhook handler (pseudocode)

function handleSlackEvent(request):
    verifySignature(request)
    body = parseJSON(request.body)

    if body.type == "url_verification":
        return { challenge: body.challenge }

    if body.type == "event_callback":
        event = body.event
        // Process event async...
        return 200  // acknowledge immediately

    if body.type == "interactive":
        // action, shortcut, or view_submission
        return 200  // ack, then use response_url for follow-up

Teams JWT validation (pseudocode)

function validateTeamsJWT(authHeader, appId):
    token = authHeader.replace("Bearer ", "")
    // Fetch keys from https://login.botframework.com/v1/.well-known/openidconfiguration
    claims = jwt_verify(token, publicKeys)
    assert claims.aud == appId
    assert claims.iss starts with "https://api.botframework.com"
    assert claims.exp > now()
    return claims

pitfalls

• Slack signature uses raw body, not parsed JSON. You must verify against the exact bytes received, not a re-serialized JSON string. Many frameworks parse the body before your handler — use middleware to capture the raw body.
• Teams serviceUrl varies by region. Don't hardcode it. The URL may be https://smba.trafficmanager.net/... or https://emea.ng.msg.teams.microsoft.com/... depending on the tenant's region.
• Bot Framework tokens expire after 1 hour. Cache the token and refresh before expiry. Don't acquire a new token for every outbound message — this adds latency and hits rate limits.
• Slack's response_url expires after 30 minutes. If you need to update a message later, use chat.update with the message ts instead.
• Teams proactive messaging requires a conversation reference. You can't just POST to a user ID — you need the conversationId and serviceUrl from a previous inbound activity. Store these on first contact.
• No Adaptive Card support via REST without the schema. You must construct the full Adaptive Card JSON yourself. Use the Adaptive Card Designer (https://adaptivecards.io/designer/) to prototype, then embed the JSON in your API calls.
• Slack interactive payload is form-encoded, not JSON. Actions, shortcuts, and view submissions arrive as application/x-www-form-urlencoded with a payload field containing JSON. Parse the payload field, not the raw body.

references

• Bot Framework REST API: https://learn.microsoft.com/en-us/azure/bot-service/rest-api/bot-framework-rest-connector-api-reference
• Slack Events API: https://api.slack.com/events-api
• Slack Web API: https://api.slack.com/web
• Slack request verification: https://api.slack.com/authentication/verifying-requests-from-slack
• Azure AD token endpoint: https://learn.microsoft.com/en-us/azure/active-directory/develop/v2-oauth2-client-creds-grant-flow
• Adaptive Card Designer: https://adaptivecards.io/designer/

instructions

Use this expert when integrating with Teams or Slack from a language that lacks a native SDK (Java for Teams, C# for Slack, Go, Ruby, etc.), or when building a lightweight integration that doesn't warrant a full SDK dependency. The patterns use pseudocode that's translatable to any language.

Pair with: cross-platform-architecture-ts.md (if also using TS for one platform), ../teams/runtime.app-init-ts.md (for TS Teams SDK comparison), ../slack/runtime.bolt-foundations-ts.md (for TS Slack SDK comparison).

research

Deep Research prompt:

"Document raw HTTP integration patterns for Microsoft Teams Bot Framework and Slack without native SDKs. Cover: Bot Framework REST Connector API (POST activities, GET conversations), Azure AD client credentials OAuth2 token acquisition, JWT validation for inbound webhooks, Slack Events API webhook setup (URL verification challenge, event_callback processing), Slack Web API methods (chat.postMessage, chat.update, views.open), Slack request signature verification (HMAC-SHA256, timing-safe comparison, timestamp validation), response_url for interaction follow-ups, Adaptive Card JSON construction for REST, Block Kit JSON construction for REST, serviceUrl caching for Teams, and rate limiting considerations."