Arcus Agent Gateway

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"] } } }

Codex (~/.codex/config.toml)

[mcp_servers.arcus]

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

</details>

ZCode : register the server and copy the agent skill

# 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"

</details>

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

Pending split warning. When pendingMultiplier is queued (non-empty) and differs from the current one, token_detail() adds a warning like pending split: 1→4.0 on 2026-11-06T00:00:00Z, and quote()'s multiplier block exposes pending + effective_time. After the split lands, raw prices jump by the ratio while *_adjusted fields stay comparable, another reason to always read adjusted values next to the multiplier.

Why a gateway and not the raw API?

api.robinhood.com/rhj + the public RPC are open, and every agent hitting them directly rediscovers the same traps:

API limits & caching

• Upstream allows 60 req/s without a key; this client self-limits to ≤ 50 req/s (a 20 ms politeness interval between requests, thread-safe).
• Transient failures (429/502/503/504, network errors) are retried up to 3 times with 2s × (attempt+1) backoff.
• Response caches (per process): /assets 5 min, /prices/{symbol} 15 s, /corporate-actions 1 h. market_status() and sector_view() are computed from caches and assets only; they never fan out 194 price requests.

On-chain sources & limits

The v0.2 on-chain tools read two keyless public sources next to the REST API. Both are free, rate-limited and partially restricted. Every tool above degrades honestly (per-field omission + warnings[] / error dicts), never with a silent empty answer.

• Public JSON-RPC (default robinhood-rpc.publicnode.com, override with ARCUS_RPC_URL): eth_call (e.g. totalSupply()) works normally. **eth_getLogs only answers inside a floating ~45–60-block window behin