> ## Documentation Index
> Fetch the complete documentation index at: https://docs.base.org/llms.txt
> Use this file to discover all available pages before exploring further.

# Balancer

> Swaps and liquidity on Balancer through shell-driven API reads, SDK calldata building, and Base MCP send_calls.

Balancer is an automated market maker for token swaps and liquidity provision. The plugin reads pool data and Smart Order Router quotes from the Balancer API, builds unsigned calldata with `@balancer/sdk`, and submits the resulting calls through Base MCP `send_calls`.

**Chains:** Base, Ethereum, Arbitrum, Optimism, and Avalanche.

**Operations:** pool discovery, swap quotes, swap execution, add liquidity, remove liquidity, and version-aware approval batching.

<Tip>
  **CLI-only plugin.** Balancer requires shell access for both reads and calldata building. It works in CLI harnesses such as Claude Code, Codex, and Cursor terminal, and does not run from chat-only surfaces.
</Tip>

## Install Balancer SDK tooling

Use a working directory with Node available:

```bash theme={null}
npm init -y
npm i @balancer/sdk viem
export RPC_URL="<a Base RPC HTTPS endpoint>"
```

The SDK simulation needs an RPC URL. The plugin spec includes the Node scripts and approval rules needed to emit Base MCP-ready calls.

## Try it

```text Swap theme={null}
Swap 100 USDC for WETH on Base through Balancer
```

```text Find yield theme={null}
What's the best Balancer pool for ETH yield on Base?
```

```text Add liquidity theme={null}
Add 500 USDC and 0.2 WETH to a Balancer pool on Base
```

## Pattern

The assistant fetches Balancer SOR paths with the API, then runs the SDK script to produce `{ chain, protocolVersion, minAmountOut, calls }`. For v2 routes, the batch includes ERC-20 approval to the Balancer Vault plus the Vault call. For v3 routes, it includes ERC-20 approval to Permit2, Permit2 approval to the router, then the router call. Native ETH input omits approvals and carries ETH in `value`.

The emitted `calls` array maps directly to Base MCP `send_calls`. The assistant reviews output, shows the approval link, and polls `get_request_status` after approval.

## Reference

<Card title="Full plugin spec on GitHub" icon="github" href="https://github.com/base/skills/blob/master/skills/base-mcp/plugins/balancer.md">
  Shell setup, GraphQL queries, SDK scripts, v2/v3 approval rules, and risk handling.
</Card>