thebrain-mcp

The first city on the Lightning Turnpike.

An MCP server that gives AI agents read-write access to a personal knowledge graph — and pays for itself with Bitcoin Lightning micropayments.

The metaphors in this project are drawn with admiration from The Phantom Tollbooth by Norton Juster, illustrated by Jules Feiffer (1961). Milo, Tock, the Tollbooth, Dictionopolis, and Digitopolis are creations of Mr. Juster's extraordinary imagination. We just built the payment infrastructure.

---

The First City

Every turnpike needs its first city. Before the booths can collect fares and the authority can stamp purchase orders, someone has to build a destination worth driving to.

thebrain-mcp is that city — a FastMCP service deployed on Horizon that bridges AI agents to TheBrain, a personal knowledge graph of 9,000+ interconnected thoughts built over a decade. Every thought, link, attachment, and note operation maps directly to TheBrain's cloud API at api.bra.in.

It's also the proving ground for Tollbooth DPYC™ — the first MCP server where every tool call is metered via Bitcoin Lightning micropayments. Pre-fund, use, top up. No subscriptions, no API keys tied to billing accounts, no fiat payment processors. The novel contribution: an MCP server architecture where the operator monetizes AI agent access through Lightning micropayments without ever pestering the client mid-conversation.

Tollbooth Credits

Tier	Cost	Examples
Read	1 sat	get_thought, search_thoughts, get_note
Write	5 sats	create_thought, create_link, update_thought
Heavy	10 sats	brain_query, get_modifications

Auth, balance checks, and credit purchases are always free. First-time users receive a seed balance on registration — enough to explore without purchasing credits up front.

BrainQuery (BQL)

A Cypher-subset query language purpose-built for TheBrain. Agents and humans express graph operations in the same formalism — full CRUD via MATCH, CREATE, SET, MERGE, and DELETE.

MATCH (n {name: "Projects"})-[:CHILD]->(m) RETURN m
MATCH (n) WHERE n.name =~ "quarterly review" RETURN n
MATCH (p {name: "Ideas"}) CREATE (p)-[:CHILD]->(n {name: "New Concept"})
MATCH (root {name: "Company"})-[:CHILD*1..3]->(d) WHERE d.name CONTAINS "Budget" RETURN d

Variable-length paths, multi-hop chains, compound WHERE with AND/OR/NOT/XOR, similarity search, and property existence checks. Full grammar in python/BRAINQUERY.md.

Getting Started

Connecting via Horizon MCP

Connect any MCP-compatible client (Claude Desktop, Cursor, your own agent) to the live endpoint:

https://personal-brain.fastmcp.app/mcp

No configuration needed — Horizon OAuth handles authentication automatically.

First Connection Walkthrough

1. session_status — Check your current session state.
2. Get a TheBrain API key at api.bra.in and find your brain ID in TheBrain's settings.
3. register_credentials(api_key, brain_id, passphrase) — Encrypts your credentials in the operator's vault. A seed balance is granted automatically.
4. list_brains → set_active_brain — Select which brain to work with.
5. brain_query — Start exploring your knowledge graph.

Returning users: call activate_session(passphrase) at the start of each session.

Self-Hosting

For local installation, configuration, and the full tool reference, see python/README.md.

To run your own instance, set these environment variables:

Variable	Purpose	Example
THEBRAIN_API_KEY	Operator's TheBrain API key (for vault access)	your-thebrain-key
THEBRAIN_DEFAULT_BRAIN_ID	Default brain ID for STDIO mode	uuid-of-brain
THEBRAIN_API_URL	TheBrain API base URL	https://api.bra.in (default)
THEBRAIN_VAULT_BRAIN_ID	Brain ID for the encrypted credential vault	uuid-of-vault-brain
BTCPAY_HOST	BTCPay Server URL for credit purchases	https://btcpay.example.com
BTCPAY_STORE_ID	BTCPay store ID	AbCdEfGh1234
BTCPAY_API_KEY	BTCPay API key with invoice + payout permissions	your-btcpay-api-key
BTCPAY_TIER_CONFIG	JSON string mapping tier names to credit multipliers	{"default": {"credit_multiplier": 1}}
BTCPAY_USER_TIERS	JSON string mapping user IDs to tier names	{"user_01KGZY...": "vip"}
SEED_BALANCE_SATS	Free starter balance for new users (0 to disable)	500

Actor Protocol

The BrainOperator class (in actor.py) satisfies OperatorProtocol from tollbooth-dpyc. It's a thin delegation layer over existing server.py tool functions.

from thebrain_mcp.actor import BrainOperator
from tollbooth import OperatorProtocol

assert isinstance(BrainOperator(), OperatorProtocol)

The actor exposes:

• slug — returns "brain" for tool-name prefixing
• tool_catalog() — returns OPERATOR_BASE_CATALOG (19 ToolPathInfo entries) — the canonical tool surface from tollbooth-dpyc

Path	Tools	Status
Hot (local ledger)	check_balance, account_statement, account_statement_infographic, restore_credits, service_status	Implemented — delegates to server.py
Hot (Secure Courier)	session_status, request_credential_channel, receive_credentials, forget_credentials	Implemented — Nostr credential delivery with credential card DM
Delegation (Authority)	purchase_credits, check_payment	Implemented — auto-certifies via MCP-to-MCP
Delegation (Authority)	certify_credits, register_operator, operator_status	Stub — connect to the Authority MCP directly
Delegation (Oracle)	lookup_member, how_to_join, get_tax_rate, about, network_advisory	Implemented — MCP-to-MCP via OracleClient

Payment processing auto-certifies via the Authority (server-to-server OAuth). Secure Courier delivers encrypted credentials via Nostr DMs with automatic credential card (ncred1...) DM-back on first receipt. Oracle community tools route directly to the DPYC Oracle — free and unauthenticated.

Architecture

The Tollbooth ecosystem is a three-party protocol spanning three repositories:

Repo	Role
tollbooth-authority	The institution — tax collection, Schnorr signing, purchase order certification
tollbooth-dpyc	The booth — operator-side credit ledger, BTCPay client, tool gating
dpyc-oracle	The concierge — community onboarding, tax rates, membership lookup
thebrain-mcp (this repo)	The first city — reference MCP server powered by Tollbooth

See the Three-Party Protocol diagram for the full architecture. The operator-side flow is also available.

Project Structure

thebrain-mcp/
├── python/                  # FastMCP server package
│   ├── src/thebrain_mcp/    # Server source, BQL engine, Tollbooth
│   ├── tests/               # Test suite (525+ tests)
│   ├── README.md            # Install, config, tools, usage
│   └── BRAINQUERY.md        # BQL grammar and reference
├── docs/
│   └── diagrams/            # Architecture and protocol flow diagrams
├── LICENSE                  # Apache License 2.0
└── NOTICE                   # Attribution notice

Prior Art & Attribution

The methods, algorithms, and implementations contained in this repository may represent original work by Lonnie VanZandt, first published on February 16, 2026. This public disclosure establishes prior art under U.S. patent law (35 U.S.C. 102).

All use, reproduction, or derivative work must comply with the Apache License 2.0 included in this repository and must provide proper attribution to the original author per the NOTICE file.

How to Attribute

If you use or build upon this work, please include the following in your documentation or source:

Based on original work by Lonnie VanZandt and Claude.ai
Originally published: February 16, 2026
Source: https://github.com/lonniev/thebrain-mcp
Licensed under Apache License 2.0

Visit the technologist's virtual cafe for Bitcoin advocates and coffee aficionados at stablecoin.myshopify.com.

Patent Notice

The author reserves all rights to seek patent protection for the novel methods and systems described herein. Public disclosure of this work establishes a priority date of February 16, 2026. Under the America Invents Act, the author retains a one-year grace period from the date of first public disclosure to file patent applications.

Note to potential filers: This public repository and its full Git history serve as evidence of prior art. Any patent application covering substantially similar methods filed after the publication date of this repository may be subject to invalidation under 35 U.S.C. 102(a).

Further Reading

The Phantom Tollbooth on the Lightning Turnpike — the full story of how we're monetizing the monetization of AI APIs, and then fading to the background.

Trademarks

DPYC, Tollbooth DPYC, and Don't Pester Your Customer are trademarks of Lonnie VanZandt. See the TRADEMARKS.md in the dpyc-community repository for usage guidelines.

License

Apache License 2.0 — see LICENSE and NOTICE for details.

---

Because in the end, the tollbooth was never the destination. It was always just the beginning of the journey.