tenderly

POST to /api/v2/project/{accountSlug}/{projectSlug}/simulate with network_id as a string, a required from address, to, input calldata, gas, and simulation_type. Use the X-Access-Key header for authentication, not Authorization Bearer.

Create a Virtual TestNet by POSTing to /vnets with fork_config containing the network_id as a number and a custom chain_id. The response includes an RPC URL supporting tenderly_setBalance, evm_snapshot, and other custom methods.

Tenderly uses the X-Access-Key header, not Authorization Bearer, so requests with Bearer tokens fail with 401. Also verify the key has not expired and has the required scope in Dashboard Settings under Authorization.

Yes, Tenderly supports 60+ EVM networks including Polygon, Arbitrum, Optimism, Base, Avalanche, BSC, and their testnets. Pass the network_id as a string like "137" for Polygon in simulation requests.

Web3 Actions have a 60-second execution timeout, 256 MB memory, and 10 MB storage per project. The runtime only includes ethers, axios, and @tenderly/actions, so arbitrary npm packages cannot be installed.

Proxy contracts and non-standard storage layouts can prevent the method from locating the balance mapping slot. Use tenderly_setStorageAt to directly write the correct storage slot, which varies by token such as slot 9 for USDC.