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Batched Contract Calls (EIP-5792)

Base MCP exposes a batched-calls tool (typically send_calls) that submits multiple contract calls for a single user approval. Use it for arbitrary contract interactions, multi-step transactions, or any flow that combines an approval with a follow-up action.
Batching is preferred whenever a flow involves a token approval followed by a protocol action (approve + deposit, approve + supply, approve + swap, etc.). Also batch whenever a plugin or protocol endpoint returns multiple transactions in a single response. Don’t split these into sequential single-send calls when one batched approval can execute them atomically.

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When to use

  • Protocol interactions not covered by send or swap (DeFi, NFT mints, approvals, governance actions).
  • Combining multiple operations into one user approval.
  • Executing a transaction array returned by a plugin’s prepare-style endpoint — pass the array straight through.

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Shape

The MCP advertises the exact parameter names and types — defer to its tool description. The general shape is:
  • A chain string (base, base-sepolia, ethereum, optimism, polygon, arbitrum, bsc, or avalanche).
  • A calls array of { to, value, data } objects:
    • to — target address, 0x-prefixed (required)
    • value — hex ETH in wei (e.g. 0x0), optional
    • data — calldata hex, optional

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Approval flow

Same as any write tool: the response returns an approval URL and request ID. See approval-mode.md.

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Generic orchestration

plugin or protocol API → { transactions: [...] } (or equivalent)
   ↓ map each transaction to a { to, value, data } call
batched-calls tool (chain, calls) → approval URL + request ID
   ↓ user approves
status-poll tool (request ID) → confirmed