Reference Implementation: GBLIN On-chain Treasury for AgentKit MCP Extensions

[gblinproject]

Language Implementation

• Python
• TypeScript

Feature Type

• Action Provider Template
• Wallet Provider Template
• Framework Extension
• Core Requirements
• Other

🚀 The feature, motivation and pitch

Context

Following the release of @coinbase/agentkit-model-context-protocol, AgentKit can now natively consume any MCP server. We've shipped a production-ready MCP server purpose-built for AgentKit-controlled wallets that need to manage treasury and pay x402 invoices on Base mainnet.

What GBLIN MCP gives AgentKit developers

The server exposes 6 tools, all read-only or calldata-only (the agent's wallet is always the sole signer):

Tool	Purpose
get_treasury_state	NAV in USD + basket composition + Crash Shield status
quote_safe_swap	Preview buy/sell with dynamic slippage buffer
swap_gblin_to_usdc_jit	JIT atomic GBLIN→USDC calldata for x402 invoices
invest_usdc_to_gblin	Convert USDC earnings into GBLIN treasury (MEV-safe minOut)
analyze_treasury_health	Balances + gas runway + rebalance recommendation
get_governance_state	Verify owner == 48h Timelock + pending ops (trust gating)

Integration is one config block

import { MCPClient } from "@modelcontextprotocol/sdk/client/index.js";
import { StdioClientTransport } from "@modelcontextprotocol/sdk/client/stdio.js";

const transport = new StdioClientTransport({
  command: "npx",
  args: ["-y", "@gblin-protocol/mcp-server"],
});
const gblinClient = new MCPClient({ name: "agentkit-agent", version: "1.0.0" });
await gblinClient.connect(transport);

// All 6 GBLIN tools now sit alongside AgentKit's native wallet tools
const { tools } = await gblinClient.listTools();

// JIT a $0.50 USDC payment for an x402 invoice in a single atomic tx
const jit = await gblinClient.callTool({
  name: "swap_gblin_to_usdc_jit",
  arguments: { usdc_needed: "0.50", wallet_address: agentKitWallet.address },
});
// → returns ready-to-broadcast calldata for AgentKit's wallet provider

Why this matters for AgentKit users

1. Real-time NAV via Chainlink ETH/USD with 24h staleness guard — agents validate treasury backing before any swap.
2. Atomic single-tx JIT swaps via the contract's native sellGBLINForToken — no batched UserOps, works on EOAs, ERC-4337 smart accounts, and EIP-7702 delegated EOAs (compatible with every AgentKit wallet provider).
3. Crash Shield monitoring — agents can detect when the basket auto-rebalances toward USDC and adjust strategy.
4. Verifiable governance — get_governance_state returns owner_is_timelock: true so agents can gate trust-sensitive actions on whether admin is fully delay-enforced (48h).

Pitch

We're submitting GBLIN MCP as a reference implementation for the AgentKit MCP extension ecosystem — useful as:

• A documentation example for "compose any MCP server with AgentKit"
• An entry in the AgentKit ecosystem / awesome-list of compatible MCP tools
• A real-world DeFi use case for the @coinbase/agentkit-model-context-protocol package

Happy to open a docs PR if helpful.

Alternatives

We considered:

1. Action Provider inside AgentKit — would require Coinbase to maintain DeFi-specific code; MCP server keeps the surface decoupled and reusable across Claude Desktop, Cursor, Windsurf, Eliza, and other MCP clients.
2. Direct Uniswap V3 calls from the agent — exposes the agent to MEV (no enforced minOut) and requires hardcoding pool fees / paths. GBLIN's native sellGBLINForToken is atomic and slippage-protected on-chain.
3. USDC-only treasury — flat zero-yield exposure; the whole point of GBLIN is to keep agent capital diversified (cbBTC + ETH + USDC) while preserving instant x402-payment capability via JIT swaps.

Additional context

Links

• MCP Registry URI: io.github.gblinproject/gblin-mcp-server
• MCP Registry listing: https://registry.modelcontextprotocol.io/v0/servers?search=gblin
• NPM package: https://www.npmjs.com/package/@gblin-protocol/mcp-server
• Repository: https://github.com/gblinproject/GBLIN-MCP
• GBLIN_V5 contract (Base mainnet): 0x38DcDB3A381677239BBc652aed9811F2f8496345
• 48h Timelock owner: 0x6aBeC8716fFeEcf7C3D6e68255b4797113E8e5Dd

Trust & verification

• All 6 tools are read-only or calldata-only — the MCP server never holds keys, never signs, never broadcasts. AgentKit's wallet provider remains the sole signer.
• Calldata returned by swap_gblin_to_usdc_jit and invest_usdc_to_gblin includes non-zero minOut values computed from on-chain quotes + dynamic slippage (2.5% normal / 4% during Crash Shield) — no sandwich-attack surface.
• GBLIN_V5 admin is enforced by a 48-hour OpenZeppelin TimelockController with immutable MIN_DELAY. Verifiable on-chain via get_governance_state.

Use case examples

• An agent earns $5 in USDC via x402-paid API calls → calls invest_usdc_to_gblin to roll earnings into the diversified index.
• An agent needs to pay a $0.50 x402 invoice but holds 95% in GBLIN → calls swap_gblin_to_usdc_jit to atomically free exactly the USDC required, paid in the same block.
• Before any treasury action, the agent calls get_governance_state and gates execution on owner_is_timelock: true.