JSON Schema 2020-12 and the Contract for Context | ​Ola Hungerford | MCP Release Party - Seattle

Session 2: Say What You Mean: JSON Schema 2020-12 and the Contract for Context ​In MCP, the schema is the contract for context. It's how a tool tells a model what goes in and what comes out. MCP originally shipped a three-keyword subset of JSON Schema, a reasonable bet on the lowest common denominator across a fragmented landscape of LLM APIs. Two SEPs later, tool schemas conform to JSON Schema 2020-12, the same default dialect as OpenAPI 3.1. This talk will cover examples of what that unlocks, what it doesn't fix, and what client and server authors need to change in the new specification. ​About Speaker: ​Ola Hungerford is a Principal Engineer at Nordstrom and a maintainer and community moderator for the Model Context Protocol. She leads AI enablement initiatives while contributing to MCP's specification, developer tooling, documentation, and community governance. Ola comes from a diverse technical background spanning two decades, including personalisation systems and enterprise platforms. She's also a vocalist and songwriter who experiments with augmenting human creativity through technology. About the Event: This session was presented at the MCP Release Party hosted on July 28th at Microsoft Reactor in Seattle area. ​This event was hosted as a part of a series of MCP Release Parties taking place simultaneously in cities around the world.