# Justin Spahr-Summers

Canonical: https://www.lazyweb.com/authors/justin-spahr-summers
Updated: 2026-09-20

MCP co-inventor and lead maintainer emeritus.

Justin Spahr-Summers co-invented the Model Context Protocol and helped establish its architecture and governance. His work is foundational reading for why MCP separates hosts, clients and servers.

Source: https://github.com/jspahrsummers

MCP governance identifies Justin as a co-inventor and lead maintainer emeritus; portrait comes from the linked public GitHub profile. Checked September 19, 2026.

## Referenced in 101

- [MCP base protocol](https://modelcontextprotocol.io/specification/2026-07-28/basic) ([MCP 101](https://www.lazyweb.com/101/mcp)) — MCP is a stateful JSON-RPC protocol with initialization, negotiated capabilities, notifications and explicit lifecycle behavior.
- [MCP server primitives](https://modelcontextprotocol.io/specification/2026-07-28/server) ([MCP 101](https://www.lazyweb.com/101/mcp)) — Servers can expose prompts, resources and tools; treating all three as interchangeable functions throws away useful protocol semantics.
- [MCP tools specification](https://modelcontextprotocol.io/specification/2026-07-28/server/tools) ([MCP 101](https://www.lazyweb.com/101/mcp)) — Tool schemas describe inputs and outputs, but the client still owns consent, presentation and safety around invocation.
- [MCP client best practices](https://modelcontextprotocol.io/docs/2026-07-28/develop/clients/client-best-practices) ([MCP 101](https://www.lazyweb.com/101/mcp)) — Clients must treat servers as untrusted capability providers, preserve user control and make tool state and failures understandable.
- [Governance and stewardship](https://modelcontextprotocol.io/community/governance) ([MCP 101](https://www.lazyweb.com/101/mcp)) — MCP uses named maintainers, decision roles and public processes rather than letting protocol direction hide inside one vendor's product roadmap.

## About this page

This is a Lazyweb reference profile, not an account, endorsement or claim that Justin Spahr-Summers contributed to Lazyweb. The profile identifies an author, editor, maintainer, speaker or source publication connected to the linked work; it is not necessarily the article byline. Summaries are Lazyweb's; the linked work remains the source of truth.