--- title: "The Protocol Learned to Stop and Ask" canonical: "https://current.tinyfish.ai/issue/40/practitioners-corner/article/33463/the-protocol-learned-to-stop-and-ask" publication: "TinyFish" publisher: "TinyFish" language: "en-US" guide: "https://current.tinyfish.ai/llms.txt" author: "Sable Whitford" author_url: "https://current.tinyfish.ai/team/201" issue: 40 section: "practitioners-corner" section_name: "Practitioner's Corner" published: 2026-07-29 updated: 2026-07-30 word_count: 290 source_links: 2 --- # The Protocol Learned to Stop and Ask *By [Sable Whitford]()* *July 29, 2026* [Read on the website]() Killing protocol-level sessions in the [2026-07-28 MCP spec](https://blog.modelcontextprotocol.io/posts/2026-07-28/) left a hole someone had to fill. Server-initiated requests used to need a held-open stream. Stateless servers don't have one. Hence multi round-trip requests. A tool call runs, hits something only a human can supply, a confirmation or a missing parameter, and returns `resultType: "input_required"` with the sub-requests attached. The client collects answers and **re-sends the original call** with them in `inputResponses`. The server picks up from there. That's the protocol's first native way to stop inside an action instead of gating in front of it. The resume is a retry. And the NSA's [May 2026 guidance](https://www.nsa.gov/Portals/75/documents/Cybersecurity/CSI_MCP_SECURITY.pdf) is blunt that idempotency "is not directly enforced by MCP," delegating it to JSON-RPC and the message queue. Whether the second send does the work twice lives in your code. The same document notes authorization in MCP is optional; plenty of implementations skip it. The spec gives you the pause. Resuming it safely is still your problem. **What else moved in 2026-07-28** - **Sessions retired:** No `initialize` handshake, no `Mcp-Session-Id`. Any request can land on any instance behind round-robin. - **Self-describing requests:** Protocol version, client identity, and capabilities ride inside `_meta` on every call. - **App state, explicitly:** Mint a handle from a tool, let the model pass it back as an argument. Visible instead of hidden in transport. - **Header routing:** `Mcp-Method` and `Mcp-Name` required on Streamable HTTP. Gateways and WAFs route without parsing bodies. - **Issuer validation:** Per RFC 9207, clients must check `iss` before redeeming a code. Credentials bind to the issuer that minted them. - **DCR deprecated:** Client ID Metadata Documents take over. DCR still works for now. - **Also out:** Roots, Sampling, Logging, and HTTP+SSE, with a twelve-month minimum offramp. ## More - [Practitioner's Corner — Issue 40]() - [Issue 40]() - [Publication guide]()