3 skill inaccuracies found during ETH wallet build (inspect content-type, port proxying, JSON-RPC params)

[riseandshaheen]

Context

While building a Cartesi Rollups v2 ETH wallet application (JS backend + React frontend) using the skills, I hit 3 issues where the skills gave incorrect or missing guidance. These caused real failures during development that required debugging to resolve.

Environment: Cartesi CLI v2.0-alpha.34, local Anvil devnet via cartesi run

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Issue 1: Inspect endpoint content type is wrong in two skills

Affected skills: cartesi-frontend (line 152), cartesi-local-dev (line 453)

Both skills instruct sending inspect requests with Content-Type: application/json and a JSON-wrapped hex payload:

# What the skills say (DOES NOT WORK with cartesi run)
curl -s -X POST "http://localhost:<port>/inspect/<app-name>" \
  -H "Content-Type: application/json" \
  -d '{"payload":"0x7374617473"}'

What actually works with cartesi run:

curl -s -X POST "http://localhost:<port>/inspect/<app-name>" \
  -H "Content-Type: application/octet-stream" \
  -d 'stats'

The inspect endpoint under cartesi run expects Content-Type: application/octet-stream with a raw string body. When you send the JSON-wrapped format, the backend's hexToString(data.payload) decodes something unexpected and route matching fails silently — the inspect returns a report but with wrong data, making it hard to debug.

Suggested fix: Update both cartesi-frontend section 5 and cartesi-local-dev Phase 4 to use application/octet-stream with raw body when targeting cartesi run.

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Issue 2: cartesi-local-dev doesn't document single-port proxying

Affected skill: cartesi-local-dev

The skill implies Anvil runs on localhost:8545 separately and uses generic <port> placeholders for inspect/RPC. In reality, cartesi run proxies all services through a single dynamic port (e.g. 6751):

Service	Actual URL
Anvil RPC	http://127.0.0.1:6751/anvil
Inspect	http://127.0.0.1:6751/inspect/<app-name>
JSON-RPC	http://127.0.0.1:6751/rpc

This matters because:

• cartesi deposit ether with --rpc-url http://127.0.0.1:8545 fails with ECONNREFUSED
• The correct flag is --rpc-url http://127.0.0.1:<port>/anvil
• Frontend config must point the wagmi RPC transport to <port>/anvil, not localhost:8545

Suggested fix: Add a clear table in cartesi-local-dev Phase 2 showing the single-port proxy layout and explicitly state that localhost:8545 is NOT directly exposed.

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Issue 3: JSON-RPC params format inconsistency between skills

Affected skills: cartesi-local-dev vs cartesi-jsonrpc

cartesi-local-dev (line 503) shows params as an array:

{"jsonrpc":"2.0","method":"cartesi_listOutputs","params":[{"application":"<app-name>"}],"id":1}

cartesi-jsonrpc (line 323) correctly shows params as an object:

{"jsonrpc":"2.0","method":"cartesi_listOutputs","params":{"application":"my-dapp"},"id":1}

The array format returns {"error":{"code":-32602,"message":"Invalid parameters"}}. Only the object format works.

Suggested fix: Update all JSON-RPC examples in cartesi-local-dev (lines 503, 508, 513, 518, 582, 599) to use object params consistent with cartesi-jsonrpc.

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Reproduction

All three issues were hit while following the skills to build an ETH deposit/withdraw app with a React frontend, targeting cartesi run on local Anvil. Happy to provide the full project if helpful.