Adding streamable HTTP transport to Healthlake MCP

[sjanjua]

Hello! I'm working on a POC using HealthLake MCP for my company, and while playing around with the codebase I added a few new features that we need for our use-case. Wanted to start a discussion here to see if my changes would be worth merging into the main upstream repo.

Here are the main changes I've made to support our use-case:

• Added the streamable HTTP transport, as specified in the official spec here: https://modelcontextprotocol.io/specification/draft/basic/transports#streamable-http
• Added a flag that allows the deployed MCP server to filter the exposed tools the client can access
• Added a flag that allows the deployed MCP server to filter exposed HealthLake datastores the client can access

I saw it mentioned somewhere that SSE were going to eventually be deprecated in favor of streamable HTTP, so I added an HTTP server that can be deployed in a cloud environment and accept HTTP connections from mcp clients. STDIO is still supported.

Once deployed to the cloud, we also need to be able to filter the exposed tools and datastores based on who the MCP server is deployed for. To support this, I added a few additional flags that allow the server to filter as needed.

Let me know what you think!