There is no official C++ SDK for MCP. So we wrote one — and ran it through the official conformance suite.

Description and use

A C++ SDK, mcp‑cpp, was built to implement the MCP 2026‑07‑28 spec, passed all official conformance tests, uncovered five real bugs, and identified a mock defect in the test harness.

Problem

MCP’s official SDK roster lacks a C++ implementation, despite C++ being the language of many data‑infrastructure systems.

Outcome

mcp‑cpp achieved 100% conformance for both server and client roles on the 2026‑07‑28 spec, uncovered five real bugs, and highlighted a mock defect in the conformance harness.

Workflow

• 1. Designed mcp‑cpp to target the 2026‑07‑28 spec, using in‑tree crypto and a single HTTP library.
• 2. Implemented server Builder, client with OAuth 2.1 support, and stdio/HTTP transports.
• 3. Ran the SDK against the official conformance suite (v0.2.0‑alpha.12) for both spec revisions and roles.
• 4. Identified and fixed five real bugs uncovered by the harness.
• 5. Baselineled expected failures and filed a mock defect upstream.
• 6. Published the SDK on GitHub and documented usage.

Evidence

mcp‑cpp implements all of it: Server: Builder with tools/resources/prompts…

Source

We didn’t self‑certify parity — we ran it against modelcontextprotocol/conformance…

Source

Running the official harness against a C++ SDK found five real bugs in days.

Source