Registry records for MCP servers in the AWS Agent Registry can go stale when a server adds a tool or changes its schema. AWS proposes a pipeline that captures UpdateAgentRuntime calls through AWS CloudTrail, routes them with Amazon EventBridge, and invokes a Lambda function that compares the server's current tools with the registry record.
The Lambda gets an OAuth bearer token through AgentCore Identity, so no client secrets are stored in its environment variables. It then calls initialize and tools/list on the MCP server, matches the record by runtime ARN, and updates the record only when the tool definitions differ. The function updates existing approved records and does not create new ones.
When a record is updated, it returns to Draft status, and consumers keep seeing the previously approved version until an administrator approves the change. The post also includes sample code and cleanup steps, and notes that automatic registration of new servers is left as a future improvement.
Why it matters if you build agents
Teams running many MCP servers can keep registry metadata current without manual edits, but each server must already have a pre-registered record with its runtime ARN embedded in the server data.
Because updates revert records to Draft, agent builders should expect a short gap before a changed tool schema becomes visible to consumers through the registry.
CloudTrail delivery can lag by about 5 to 15 minutes, so the registry may not reflect a new tool immediately after deployment.
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