Lexicon

Lexicon is a schema definition language used to describe evermeet records, HTTP endpoints (XRPC), and event stream messages.

We are currently using the Lexicon definition language version 1 specification as defined by the AT Protocol.

The schema language is similar to JSON Schema and OpenAPI.

Namespaced Identifiers (NSIDs)

Namespaced Identifiers (NSIDs) are used to reference Lexicon schemas for records, XRPC endpoints, and more.

The basic structure and semantics of an NSID are a fully-qualified hostname in Reverse Domain-Name Order, followed by a simple name. The hostname part is the domain authority, and the final segment is the name.

For example:

• app.evermeet.object.getProfile
• app.evermeet.auth.createSession
• app.evermeet.server.describeServer

→ Full NSID Syntax specification

Libraries

• @atproto/lexicon (TypeScript) - schema validation library
• atproto-lexicon (PHP) - A PHP-based Lexicon parser