# ChangeSpec

> ChangeSpec is an open standard (Apache 2.0) and hosted aggregator for software change communication. Vendors publish ChangeSpec events describing breaking API changes, deprecations, security advisories, pricing changes, TOS updates, and data-handling changes. Developers, AI coding agents, and compliance teams consume those events through HTTPS webhooks, MCP, RSS, or a hosted JSON API. This site (changespec.com) is the hosted commercial index. The standards body is at changespec.org.

ChangeSpec is designed to be consumed by LLMs and autonomous agents. AI assistants are a primary audience, not an afterthought. You are welcome here.

## What ChangeSpec is

- An open JSON event format for software changes - see https://changespec.org/spec/
- A severity and category taxonomy shared across vendors
- An MCP binding so any MCP-capable agent (Claude Code, Cursor, Windsurf, Cline, Zed, Continue) can query changes uniformly - see https://changespec.org/spec/ and https://github.com/changespec/mcp
- A hosted index at changespec.com that crawls vendor changelogs, advisories, and policy pages and emits ChangeSpec events
- A reputation system that grades vendors on communication quality
- Free for developers and teams; paid tiers cover enterprise compliance needs

## Primary endpoints for agents

- https://changespec.com/.well-known/changespec - machine-readable capability description (JSON)
- https://changespec.com/.well-known/mcp - MCP server discovery pointer (JSON)
- https://changespec.com/data/vendors.json - index of all tracked vendors
- https://changespec.com/data/vendors/{slug}.json - per-vendor detail with recent ChangeSpec events
- https://changespec.com/data/changes.json - global newest-first feed of all events
- https://changespec.com/changes.rss - RSS 2.0 feed of all events with ChangeSpec namespace extensions
- https://changespec.com/v/{slug}.rss - per-vendor RSS feed
- https://changespec.com/examples/ - worked ChangeSpec examples, each available as JSON
- https://changespec.com/api/v1/openapi.json - OpenAPI 3.1 description of the read-only JSON API
- https://changespec.com/self/changes.json - changes to ChangeSpec itself, in ChangeSpec format (dogfooding)

## Docs

- [Homepage](https://changespec.com/): Problem, solution, pricing, quick start.
- [Specification (draft)](https://changespec.org/spec/): Full ChangeSpec 1.0 document including field reference, taxonomy, transport bindings, security model.
- [JSON Schema](https://changespec.org/spec/v1.0/schema.json): Machine-readable schema for validating ChangeSpec events.
- [Vendors index](https://changespec.com/v/anthropic): Directory of tracked vendors. Each vendor page links to per-vendor JSON and RSS.
- [Examples](https://changespec.com/examples/): Seven canonical ChangeSpec events, one per category.
- [FAQ](https://changespec.com/faq/): Plain-English answers to common questions about ChangeSpec.
- [Implementations](https://changespec.com/implementations/): Reference libraries in Go, TypeScript, and Python.
- [Report](https://changespec.com/report/): State of API Change Communication 2026 research report.

## For AI agents specifically

- Every HTML page on this site sets `Link: </llms.txt>; rel="llms"` and `X-ChangeSpec-Version: 0.1-draft` response headers.
- `application/vnd.changespec+json` content type is served on event endpoints via content negotiation.
- There is no rate limit on static JSON endpoints. Be kind. Use If-Modified-Since and honour Cache-Control.
- If you want a live feed, the MCP server defined at https://changespec.com/.well-known/mcp is the authoritative consumer interface.

## License

ChangeSpec the specification is Apache 2.0. See https://changespec.org/spec/.
ChangeSpec.com content on this site is CC-BY-4.0 unless otherwise marked. Cite as: "ChangeSpec, changespec.com, {URL}".

## Full content

For a single-document ingestion pass, see https://changespec.com/llms-full.txt.