# Justin Spahr-Summers

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

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 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) — 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) — 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) — 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 uses named maintainers, decision roles and public processes

[Justin Spahr-Summers](<https://www.thelazyweb.com/authors/justin-spahr-summers/>)

Source observed: 2026-09-20T21:38:42.441Z. Last checked: 2026-10-08T02:01:25.854+00:00.

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