Build with Kern.

• Learn what Kern offers for training, sleep, recovery, nutrition, and daily planning.
• Find published Kern articles and sources to explain general fitness and recovery concepts.
• Find the iPhone beta invitation, support contact, and privacy information.

No API key is required for the public endpoints. They provide product information and published knowledge articles. Personal account, health, and training data remain private. These interfaces cannot sign in, edit accounts, or act on a person’s behalf.

Use bounded queries and pagination, cache repeated reads, and avoid repeatedly retrying failed requests.

Base URL: https://www.joinkern.com. OpenAPI 3.1 specification · Endpoint discovery.

• GET /api — public endpoint discovery.
• GET /api/v1/site — product, features, integrations, download, and support information.
• GET /api/v1/knowledge — list or search published articles. Optional parameters: q (up to 120 characters), category, limit (1–50, default 20), and offset (0–10000, default 0).
• GET /api/v1/knowledge/{category}/{slug} — published article metadata, canonical URL, and Markdown content.

Categories: sleep, recovery, training, nutrition, health, running, cycling. Search matches all query terms across titles, descriptions, excerpts, and tags. Pagination returns items, total, limit, and offset.

curl 'https://www.joinkern.com/api/v1/site'

curl 'https://www.joinkern.com/api/v1/knowledge?q=HRV&limit=5'

curl 'https://www.joinkern.com/api/v1/knowledge/sleep/how-to-improve-sleep-quality'

curl -H 'Accept: text/markdown' 'https://www.joinkern.com/'

Errors use application/problem+json with status, code, detail, resolution, and a documentation link. Invalid parameters return 400, missing resources return 404, and unsupported methods return 405. A temporary outage returns 503 with a Retry-After header.

Connect a Streamable HTTP client to https://www.joinkern.com/mcp. No API key or session is required. The server is stateless and provides three read-only tools: get_kern_info, search_kern_knowledge (q, category, limit, offset), and get_kern_article (category, slug).

POST JSON-RPC messages with Content-Type: application/json and Accept: application/json, text/event-stream. Initialize with protocol version 2025-11-25, 2025-06-18, or 2025-03-26, then send notifications/initialized. Include the negotiated MCP-Protocol-Version on subsequent requests.

Tool results contain structured public data and text. The server does not send unsolicited SSE events, so GET returns 405. Use a server-side MCP client; cross-origin browser connections are not supported. MCP discovery manifest.

Request the homepage, docs, About, Contact, knowledge pages, or public profiles with Accept: text/markdown to receive Markdown. HTML and Markdown responses vary by Accept. Unknown documents return a real 404 with links to helpful resources.

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