mcp-inspector-testing

mcp-inspector-testing skill

Test server-facing Wassette changes with the MCP Inspector before committing. This confirms the server starts, tools are exposed over MCP, tool calls behave as expected, and no regressions slipped in.

Workflow

1. Build your changes: just build.
2. Start the server (Terminal 1): just run, or an example such as just run-fetch-rs. The server listens at 127.0.0.1:9001/mcp over Streamable HTTP.
3. Drive it with the Inspector (Terminal 2) — always run tools/list first.
4. Capture Inspector output when it helps demonstrate or debug the change.

Running the server

just run                       # Default server
just run RUST_LOG='debug'      # Verbose logs
just run-filesystem            # Example: filesystem component
just run-fetch-rs              # Example: fetch component
just run-memory                # Example: memory component
just run-get-weather           # Example: weather (needs OPENWEATHER_API_KEY)

Inspecting with the MCP Inspector

BASE=http://127.0.0.1:9001/mcp

# List capabilities (run tools/list first)
npx @modelcontextprotocol/inspector --cli $BASE --transport http --method tools/list
npx @modelcontextprotocol/inspector --cli $BASE --transport http --method resources/list
npx @modelcontextprotocol/inspector --cli $BASE --transport http --method prompts/list

# Call a tool
npx @modelcontextprotocol/inspector --cli $BASE --transport http \
  --method tools/call --tool-name mytool --tool-arg key=value

# Multiple args, or JSON for complex parameters
npx @modelcontextprotocol/inspector --cli $BASE --transport http \
  --method tools/call --tool-name mytool --tool-arg key1=v1 --tool-arg key2=v2
npx @modelcontextprotocol/inspector --cli $BASE --transport http \
  --method tools/call --tool-name mytool --tool-arg 'options={"format":"json","max_tokens":100}'

# Custom headers (e.g. auth testing)
npx @modelcontextprotocol/inspector --cli $BASE --transport http \
  --method tools/list --header "X-API-Key: your-api-key"

Capturing output

npx @modelcontextprotocol/inspector --cli $BASE --transport http \
  --method tools/list > inspector-output.txt

Include captured output in review notes or issue comments when it helps demonstrate a fix.

Troubleshooting

1. Confirm just run started without errors.
2. Run tools/list to see what is actually exposed.
3. Re-run the server with RUST_LOG=debug for detailed logs.
4. Start with simple tool calls, then add argument complexity.
5. Compare against a known-good example such as fetch-rs.