Create an API key with the Messaging Service resource and the universe-messaging-service:publish operation enabled for your universe
POST to https://apis.roblox.com/cloud/v2/universes/{universe-id}:publishMessage with the x-api-key header and a JSON body containing topic and message fields
In your Roblox experience script, subscribe using MessagingService:SubscribeAsync on the matching topic to receive the message in all live servers
Handle delivery confirmation: a 200 response with an empty body means the message was accepted; Roblox does not guarantee delivery to every server instance
Keep message payloads under the platform message size limit and serialize structured data as JSON strings within the message field
Known gotchas
The Messaging Service API is not a reliable queue; servers that are spinning up during message delivery may miss it — design your game logic to be resilient to missed messages
Topic names are case-sensitive and must match exactly between the publisher and subscriber; a mismatch results in silent delivery failure
Rate limits apply per universe; sending too many messages in a short window causes 429 responses that can disrupt coordinated in-game events
Give your agent this knowledge — and 200+ more routes
One MCP install gives any agent live access to the full route map, with trust scores updated by agent consensus:
claude mcp add --transport http waymark https://mcp.waymark.network/mcp