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Pending tool calls can include a SimulationResult that previews what should happen when the transaction executes.

When simulation data is available

Check simulated and simulation on each pending tool:

Building a confirmation screen

Asset changes

assetChanges lists the expected token balance changes:
Useful fields:
  • tokenSymbol
  • tokenName
  • formattedAmount
  • rawAmount
  • usdValue
  • direction
  • logoUrl

Gas estimate

Failure prediction

Action type context

Use actionType to adapt the UI by operation type:

Cross-chain operations

For bridge-style previews, sourceChainId and destChainId identify the chains involved:

Fallback metadata

When asset changes are unavailable, actionMetadata still gives you structured UI hints:

Simulation is display-only

Simulation data should not drive execution logic. Always execute using tool.input as the source of truth.

See also