Concept card

Model Context Protocol (MCP) — Specification Deep Dive

As of 2026-07-24T14:00:00Z

Edited by Cédric-Olivier Mâry, sole editor and publication director — 27 years in the SAP ecosystem. How these pages are produced, and where automation is used.

What is Model Context Protocol (MCP) — Specification Deep Dive?

MCP's capability negotiation handshake means a client must never assume an undeclared capability — a server that omits "resources" makes any resources/list call by the client a protocol violation, not a graceful no-op.

The Model Context Protocol is a precise, versioned contract that governs how an AI agent talks to the outside world — the databases, business applications, and tools it needs to actually get work done rather than just talk about it. For an SAP analytics practitioner, understanding the protocol machinery itself, not just the fact that Joule or another assistant "supports MCP," is what separates someone who can evaluate a vendor's integration claims from someone who has to take them on faith.

What the protocol actually is

MCP is built on JSON-RPC 2.0, the same lightweight remote-procedure-call format that already powers the Language Server Protocol behind modern code editors. Every message is a plain JSON object carrying a method name, optional parameters, and, for requests that expect an answer, an identifier used to match the response back to the call. The choice is deliberate rather than incidental: JSON-RPC is widely implemented, has predictable and structured error handling, and does not care what pipe it travels over — the identical message format works across a local process pipe, a web-based streaming connection, or a persistent socket. That transport independence is what lets the same protocol serve a developer's laptop and a production multi-tenant deployment without redesigning the message layer.

Why it matters

Built on JSON-RPC 2.0 (the same format as the Language Server Protocol), MCP inherits predictable structured error semantics and transport-agnosticism across stdio, SSE, or WebSocket.
The initialize handshake forces both client and server to declare capabilities explicitly, making the protocol forward-compatible — new capability types degrade gracefully on older clients.
Tools are the highest-risk primitive because a tools/call can write data or trigger irreversible workflows — schema quality on this primitive matters more than on resources or prompts.

Key points

JSON-RPC 2.0 wire format — requests, responses, notifications; spec revision pinned to 2025-06-18 as of mid-2026.
Two transports — stdio for local (Claude Desktop, Cursor, SAP Build local server) and Streamable HTTP for remote (replaces the earlier SSE-only draft).
Three-phase session — initialize (protocol version + capabilities) → notifications/initialized → feature calls until close.
Capability negotiation — tools, resources, prompts, sampling, roots; what each side declares constrains what the other can ask.
Adopted by SAP, OpenAI, Google, Microsoft — the single cross-vendor surface; Analytics Legends MCP server is the internal reference implementation.
Model Context Protocol (MCP) — Specification Deep Dive is mastered only when it changes a named buyer decision.
Start with the semantic contract and control model before demonstrating the tool.
Use current SAP, analyst, study, KG, and news signals as evidence, not decoration.
Separate verified facts from directional trends and modeled assumptions.
Define owner, metric, threshold, support path, and rollback before scaling.

Terms used on this page

JSON-RPC 2.0: Lightweight remote-procedure-call protocol over a bidirectional byte stream; defines request, response and notification message shapes that MCP layers its semantics on top of.
Streamable HTTP transport: MCP's remote transport since the 2025-06-18 revision; a single HTTP endpoint accepts JSON-RPC POSTs and may upgrade to a server-sent-event stream for progressive responses, with session continuity via Mcp-Session-Id.
Capability negotiation: The initialize-time exchange in which client and server declare which optional features (tools.listChanged, resources.subscribe, sampling, roots, prompts) they support; calls outside the negotiated set must be refused.
Initialize handshake: The mandatory first exchange of an MCP session: client sends initialize with protocolVersion and capabilities, server responds, client sends the notifications/initialized notification, then normal calls may begin.
Decision owner: The accountable person who accepts the trade-off and funds the next action.
Semantic contract: The shared definition of business terms, metrics, entities, and access rules used by tools and teams.
Control plane: The layer that applies policy, access, lineage, monitoring, and escalation across the operating model.
Evidence grade: A label that separates verified fact, directional signal, modeled assumption, and field observation.

Sources

Full card available to members. What the full card adds: the full decision framework · the SAP vs Snowflake / Databricks / Fabric comparison · the common pitfalls and their fix · the cheat sheet · the architecture schemas · the code blocks · the facts worth quoting.

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