arcus-agent-gateway

Robinhood Chain (Arcus) carries 194 tokenized US equities on-chain, and its public API answers questions most people don't think to ask: who actually holds AAPL, what a wallet's stock portfolio looks like, which way the whales moved NVDA today. This MCP server hands all of that to an AI agent. Read-only, keyless, no writes; every tool is a GET against api.robinhood.com/rhj plus two public on-chain sources, cached and rate-limited so an enthusiastic agent can't hammer the upstream.

Use cases

Ask it who holds AAPL and you get the top holder addresses with their share of total supply, flagged contract or wallet. One holder contract turns out to sit on 35% of NVDA; that is the kind of concentration risk a quote page will never show you.

wallet_holdings reads any address across all 194 equities and values the positions it has fresh quotes for. transfer_history walks recent ERC-20 Transfers with a min_value filter, which is how you catch the large prints instead of the dust.

Prices are the trap here, so they ship split-safe: raw and multiplier-adjusted values travel together on every quote, and a pending split (NVDA queues a 4.0 multiplier for 2026-11) comes with a warning and the effective time. A morning scan of market health, halted tokens and 13-sector averages costs two cheap calls.

Full walkthroughs with real outputs: examples/use-cases.md.

Quickstart

Claude Code:

claude mcp add arcus -- uvx arcus-agent-gateway

Run over stdio (the default, for local agents):

uvx arcus-agent-gateway

Standard config for Claude Desktop / Cursor (claude_desktop_config.json / .cursor/mcp.json):

{
  "mcpServers": {
    "arcus": {
      "command": "uvx",
      "args": ["arcus-agent-gateway"]
    }
  }
}

[mcp_servers.arcus]
command = "uvx"
args = ["arcus-agent-gateway"]

# 1) start the gateway (keep it running)
uvx arcus-agent-gateway --http --port 8902 &

# 2) register it (merges into ~/.zcode/cli/config.json; workspace .zcode/config.json works too)
python3 - <<'PY'
import json, os
p = os.path.expanduser("~/.zcode/cli/config.json")
os.makedirs(os.path.dirname(p), exist_ok=True)
cfg = json.load(open(p)) if os.path.exists(p) else {}
cfg.setdefault("mcp", {}).setdefault("servers", {})["arcus"] = {
    "type": "http", "url": "http://127.0.0.1:8902/mcp"}
json.dump(cfg, open(p, "w"), indent=2)
print("arcus MCP server registered:", p)
PY

# 3) copy the agent skill (tool guide + watchlist cron recipe)
git clone -q --depth 1 https://github.com/alekskram/arcus-agent-gateway /tmp/aag
cp -r /tmp/aag/.agents/skills/arcus-gateway ~/.zcode/skills/ && rm -rf /tmp/aag
echo "ZCode setup done, restart your session and call any arcus tool"

Hosted form, streamable HTTP on port 8902:

uvx arcus-agent-gateway --http               # 127.0.0.1:8902
curl http://127.0.0.1:8902/health            # -> {"ok": true, "service": "arcus-agent-gateway"}

Tools

All 13 tools are read-only (annotated readOnlyHint: true). Names and parameters are exactly as registered by arcus_mcp/server.py.

Multiplier logic (read this before using prices)

Robinhood Chain tokens carry a multiplier, the corporate-action adjustment factor for the token contract (1.0 = untouched). Splits change it; for example NVDA's 2026-11 split queues pendingMultiplier: "4.0".

• The REST API returns RAW prices. bid/ask from /prices/{symbol} are in token-contract units and are not multiplier-adjusted.
• Adjusted values are computed by this server, never taken from upstream: price_adjusted = round(price_raw × currentMultiplier, 6).
• Raw and adjusted always travel together. Every quote carries bid_raw/ask_raw/spread_raw and bid_adjusted/ask_adjusted/ mid_adjusted next to the multiplier block, never one without the other.
• On-chain quantities (token balances, mint/burn volumes) are natively in adjusted (multiplied) units; REST prices are not. If you compare the two, go through the *_adjusted fields.

Worked example (live fixture, 2026-09-03):

AAPL   currentMultiplier = 1.000566080061092436
       bid_raw   = 327.77   →  bid_adjusted = round(327.77 × 1.000566…, 6) = 327.955544
       ask_raw   = 327.78   →  ask_adjusted = 327.965550
       mid                      mid_adjusted = 327.960547