DriftGuard

Catch API and schema changes before your integrations break.

Start hosted trial (no credit card): driftguard.org/start — full Pro on one endpoint, ~2 minutes.
10-min MCP drift lab: Dev.to tutorial · ToolSchema Kit

DriftGuard compares JSON contracts locally (free CLI and MCP client) and runs scheduled checks with alerts when you need always-on API contract monitoring and contract observability on hosted Pro/Team.

Use schema drift CI (compare_json, GitHub Actions) before merge; use hosted watches when you need MCP tool catalog drift detection in production.

Not full self-host: this repo is the client layer (diff + MCP connector). The monitoring pipeline is a managed service — see OPEN_CORE.md.

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Why this repo?

	This repo (OSS client)	Hosted DriftGuard
Goal	Test locally, integrate with agents	Production monitoring
Diff JSON schemas	✅ CLI + MCP	✅ + history
Parse mcp.json preview	✅ offline	✅ + auto-import
Continuous checks	❌	✅ cron + queues
MCP tools/list polling	❌	✅
Alerts & console	❌	✅

Use the OSS client to try and integrate. Upgrade when you need always-on monitoring.

CI: one-file starter — examples/workflows/driftguard-starter.yml · GitLab — docs/GITLAB_CI.md · GitHub Marketplace path — docs/GITHUB_MARKETPLACE.md

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Quick start

git clone https://github.com/kioie/driftguard
cd driftguard && npm ci && npm run build

CLI

npm run check -- diff '{"id":1,"email":"a@b.com"}' '{"id":1}'
# exit 1 if breaking changes

MCP server (Cursor, Claude, Windsurf)

See docs/QUICKSTART.md, examples/mcp-client-config.json, and examples/AGENTS-snippet.md for consumer repos.

{
  "mcpServers": {
    "driftguard": {
      "command": "node",
      "args": ["/absolute/path/to/driftguard/dist/mcp/server.js"]
    }
  }
}

Add "DRIFTGUARD_API_KEY": "dg_…" under env for monitoring tools.

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MCP tools

Tool	API key	Purpose
compare_json	No	Local before/after JSON schema diff
parse_mcp_config	No	Preview watch URLs from mcp.json (no create)
hosted_info	No	Offline vs hosted matrix, trial/pricing links
explain_drift	No	Remediation hints for breaking changes
register_watch	Pro	Continuous monitoring
check_watch	Pro	Immediate check
list_watches	Pro	List watches
list_drift_events	Pro	Drift history
suggest_watches	Pro	Import mcp.json + optional create
assert_coverage	Pro	CI gate — deps must be watched

Agents: read SYSTEM_PROMPT.md for when-to-use guidance.

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CI integration

Pin the client version and follow the hook → preview → trial → gate funnel:

# 1. Hook (free)
- uses: kioie/driftguard/.github/actions/drift-diff@v0.3.2
  with:
    before: '{"id":1}'
    after: '{"id":1,"name":"x"}'

# 2. Preview (free — links to console, non-blocking)
- uses: kioie/driftguard/.github/actions/drift-coverage-preview@v0.3.2
  with:
    files-json: '[{"path":"mcp.json","content":"..."}]'

# 3. Gate (Pro API key — blocks until all deps watched)
- uses: kioie/driftguard/.github/actions/drift-coverage@v0.3.2
  with:
    api-key: ${{ secrets.DRIFTGUARD_API_KEY }}
    files-json: '...'

Full model: docs/CI.md

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1. Try offline — compare_json, parse_mcp_config in Cursor (no signup)
2. Start trial — driftguard.org/start (full Pro on one endpoint)
3. Add API key — set DRIFTGUARD_API_KEY in MCP env → monitoring tools unlock
4. Team — pricing for more watches, audit export, SSO

Advanced (rare): override hosted URL with DRIFTGUARD_API (default https://driftguard.org). Non-default values require DRIFTGUARD_ALLOW_CUSTOM_API=1 — otherwise the client pins to the official host so a malicious MCP config cannot exfiltrate your API key.

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Project structure

src/core/          # Schema inference + diff (MIT)
src/cli/           # driftguard diff | mcp
src/mcp/           # MCP server (local + hosted proxy)
examples/          # MCP client config template
docs/              # Documentation hub, quick start, reference
AGENTS.md          # Agent contribution guide
SYSTEM_PROMPT.md   # Agent tool reference
server.json        # MCP Registry metadata
OPEN_CORE.md       # Public vs hosted boundary

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For AI agents

Doc	Use
docs/README.md	Documentation hub — pillars, OSS vs hosted, nav
SYSTEM_PROMPT.md	Tool matrix, decision flow, config
docs/getting-started.md	Progressive onboarding funnel
docs/reference/	MCP + CLI reference index
docs/CI.md	Version-pinned CI paths (Actions, npx, assert)
AGENTS.md	Editing this repo
docs/QUICKSTART.md	Setup steps

Call MCP tool hosted_info at runtime for current URLs and capability matrix.

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Design

Brand kit: docs/DESIGN.md

Contributing

CONTRIBUTING.md — public client only.

License

MIT — LICENSE. Applies to this repository only; hosted service is separate.