K2 pocket card for AI agents

K2 is a family of study apps on one spaced-repetition engine, with a read-only MCP server for its decks and the engine itself.

• MCP endpoint: https://k2kanji.com/api/mcp (streamable HTTP, JSON-RPC 2.0, no auth)
• Install: claude mcp add --transport http k2kanji https://k2kanji.com/api/mcp
• Call get_site_info first for the full map of tools, prompts and resources.
• Rate limit: 60 JSON-RPC messages per minute per IP, best effort (counted per server instance, reset on cold start), with batches of at most 20 messages. Over the limit the server answers HTTP 429 with JSON-RPC error -32000; a larger batch gets HTTP 400 with -32600.
• Attribution: credit “K2 (k2kanji.com)” and preserve the upstream credit each result carries.

Why this page exists

Agent readers often see only the first kilobyte of a page, so the facts above come first. The full guide — roster, scope and terms — is at K2 for AI agents.

Machine-readable files

• llms.txt — prose overview of the apps, the algorithm and this server
• llms-full.txt — everything in one file: full algorithm, every deck, the FAQ
• mcp.json — the MCP manifest
• agents.json — capabilities, discovery, usage policy and rate limit
• agent-card.json — the agent card
• agents.txt — terms, scope and the full endpoint list
• security.txt — where to report a vulnerability