Second Brain

Second Brain — setup and usage

Author: Moran Koren, Ben-Gurion University of the Negev (korenmor@bgu.ac.il). Part of the Theorist Toolbox.

Sets up a self-contained agentic-RAG library in a target directory: papers are ingested from LaTeX source (preferred), HTML, or PDF-OCR into a chunked, QA-gated index; an agent (or Claude Code itself via MCP) answers questions by reading exact theorems/proofs with custom macros and prerequisite definitions auto-bundled. Full design: package/ in this skill contains the complete brain Python package.

Throughout, $SKILL means this skill's base directory (shown in the message that loaded this file) and $TARGET means the directory the user wants the second brain in (default: the current working directory; ask only if the cwd is clearly wrong for a paper library, e.g. a code repo).

Step 0 — detect state

$TARGET/config.toml exists AND $TARGET/.venv/bin/brain runs → already initialized: skip to Usage. Otherwise run Init.

Init

bashCopy code
cd "$TARGET"
python3 -m venv .venv
.venv/bin/pip install -q "$SKILL/package[dev,providers,mcp,web]"
cp "$SKILL/templates/config.toml" config.toml
.venv/bin/brain status        # creates papers/ parsed_papers/ index/ scratchpad/

Then register the MCP server for Claude Code by writing $TARGET/.mcp.json (absolute paths, no ~):

jsonCopy code
{
  "mcpServers": {
    "second-brain": {
      "command": "<ABS_TARGET>/.venv/bin/python",
      "args": ["-m", "brain.mcp_server"],
      "env": { "BRAIN_CONFIG": "<ABS_TARGET>/config.toml" }
    }
  }
}

Verify the install with the bundled fixture, then remove the test entry:

bashCopy code
.venv/bin/brain ingest "$SKILL/package/tests/fixtures/mini_paper" --id selftest --no-llm
.venv/bin/brain search "monotone valuations"       # selftest must rank first
.venv/bin/python -c "
from pathlib import Path; from brain.config import load_config; from brain.index import store
import shutil
cfg = load_config(Path('config.toml')); idx = store.load_index(cfg.index_file)
idx.pop('selftest', None); store.save_index(cfg.index_file, idx)
shutil.rmtree(cfg.parsed_dir / 'selftest', ignore_errors=True)"

Finish by telling the user: (1) init is done and verified; (2) restarting Claude Code in $TARGET and approving the "second-brain" MCP server lets them ask about their library in any session, billed to their Claude subscription; (3) the standalone CLI default (claude-code provider) also uses the subscription — keep ANTHROPIC_API_KEY unset for that; and (4) offer to ingest papers right away (see below). If the directory already contains PDFs or .tex sources, list them and offer to ingest them.

Usage

All commands run from $TARGET with .venv/bin/brain:

• Ingest — brain ingest <arxiv-id | tex-dir | file.tex | url | file.pdf>
  • Prefer arXiv ids / LaTeX source (Tier 0: exact math, no OCR). PDFs need pip install "$SKILL/package[ocr]" and are QA-flagged by default.
  • Idempotent; add --force to re-ingest, --no-llm to skip metadata enrichment (use --no-llm when the user wants speed or determinism).
  • After a batch, run brain status and report any ⚠ needs_review papers.
• Search (no LLM) — brain search "query" -v
• Ask — brain ask "question" -v (or brain repl for multi-turn). Inside Claude Code, prefer the MCP tools directly instead of shelling out to brain ask — same backend, no nested agent.
• Health — brain status; run .venv/bin/pytest "$SKILL/package/tests" -q if something seems broken.

When answering from MCP tools yourself, follow the library's grounding rules: search first; use read_theorem_or_proof for any formal statement; record notation with write_to_scratchpad after reading a Model section; cite [paper_id, Item] for every mathematical claim; flag needs_review sources.

Updating the bundled package

If the canonical copy in papers_2nd_brain evolves, refresh this skill with: rsync -a --exclude __pycache__ --exclude '*.egg-info' <canonical>/pyproject.toml <canonical>/src <canonical>/tests "$SKILL/package/" — then existing brains pick it up via .venv/bin/pip install -q --force-reinstall "$SKILL/package[dev,providers,mcp,web]".