Tool selection fails with error

[ducile]

Inspector Version

0.17.2

Describe the bug After listing the tools and selecting one of the implemented tools in the UI, the web-app turns black with following error: index-Bl2jgoAl.js:3970 TypeError: Cannot use 'in' operator to search for 'default' in string

To Reproduce Steps to reproduce the behavior:

1. Connect to MCP server
2. Click on tools
3. Select one of the tools
4. Screen turns black and DevTools show error

Expected behavior It should show an input field to receive a text input

Screenshots If applicable, add screenshots to help explain your problem.

Environment (please complete the following information):

• OS: Mac OS
• Browser: Chrome

Additional context Add any other context about the problem here.

[olaservo]

Hi @ducile I wasn't able to repro with the demo server @modelcontextprotocol/server-everything@latest, could you share which server you're testing with when this happens? I'm wondering if your tool's input schema is malformed.

[ducile]

Hi @olaservo , I'm using the latest @modelcontextprotocol/inspector and have connected it with my local MCP server. The project was setup using Kotlin Multiplatform. My tool input is configured as follows:

server.addTool( name = "send-confluent-platform-version-upgrade-information", description = """ Sends information about version upgrades. """.trimIndent(), inputSchema = Tool.Input( properties = JsonObject( mapOf( "changeNumber" to JsonPrimitive("string"), "currentVersion" to JsonPrimitive("string"), "newVersion" to JsonPrimitive("string"), "upgradePlan" to JsonPrimitive("string"), "linkToReleaseNotes" to JsonPrimitive("string") ) ), required = listOf("changeNumber", "currentVersion", "newVersion", "upgradePlan", "linkToReleaseNotes") )

[below]

I had the same issue and solved it, here is a sample server

You need to make sure to adhere to the latest specification, the property name is now a key, and the description and type are nested within it