# Lotus: API troubleshooting

This page offers some troubleshooting advice for Lotus API users by listing some of the most common errors that they can come accross.

Have you successfully overcome other API-related problems? Please contribute to this page by editing it with the link at the bottom!

# Types: params

params must be an array. If there are no params you should still pass an empty array.

# Types: TipSet

For methods such as Filecoin.StateMinerPower, where the method accepts the argument of the type TipSet, you can pass null to use the current chain head.

curl -X POST \
     -H "Content-Type: application/json" \
     --data '{ "jsonrpc": "2.0", "method": "Filecoin.StateMinerPower", "params": ["t0101", null], "id": 3 }' \
     'http://127.0.0.1:1234/rpc/v0'

# Types: Sending a CID

If you do not serialize the CID as a JSON IPLD link (opens new window), you will receive an error. Here is an example of a broken CURL request:

curl -X POST \
     -H "Content-Type: application/json" \
     --data '{ "jsonrpc": "2.0", "method":"Filecoin.ClientGetDealInfo", "params": ["bafyreiaxl446wlnu6t6dpq4ivrjf4gda4gvsoi4rr6mpxau7z25xvk5pl4"], "id": 0 }' \
     'http://127.0.0.1:1234/rpc/v0'

To fix it, change the params property to:

curl -X POST \
     -H "Content-Type: application/json" \
     --data '{ "jsonrpc": "2.0", "method":"Filecoin.ClientGetDealInfo", "params": [{"/": "bafyreiaxl446wlnu6t6dpq4ivrjf4gda4gvsoi4rr6mpxau7z25xvk5pl4"}], "id": 0 }' \
     'http://127.0.0.1:1234/rpc/v0'