I'm looking to integrate an MCP server that I've b...

# koog-agentic-framework

[John O'Reilly]

I'm looking to integrate an MCP server that I've been successfully using. with Claude Desktop but getting....

ai.koog.agents.mcp.McpToolRegistryProvider - Failed to parse descriptor parameters for tool: get-emissions
java.lang.IllegalArgumentException: Parameter countryCode must be a JSON object

[John O'Reilly]

The MCP server is developed using Kotlin MCP SDK and includes

server.addTool(
        name = "get-emissions",
        description = "List emission info for a particular country",
        inputSchema = Tool.Input(
            properties = JsonObject(
                mapOf(
                    "countryCode" to JsonPrimitive("string"),
                    "year" to JsonPrimitive("date"),
                )
            ),
            required = listOf("countryCode", "year")
        )

[Didier Villevalois]

It doesn't look to me like this is a valid JSON schema. But I may be wrong.

I think each property here should be a valid JSON schema type definition. Something like { "type": "string" }.

So the whole thing should look like:

properties = JsonObject(
  mapOf(
    "countryCode" to JsonObject(
      mapOf("type" to "string")
    ),
    "year" to JsonObject(
      mapOf("type" to "date")
    ),
  )
),

(the "required" part looks correct to me)

It would appear that Claude can accept invalid schema definitions...

[John O'Reilly]

ok, thanks, I'll try that shortly

[John O'Reilly]

ok, this is what ended up working here

properties = buildJsonObject {
    putJsonObject("countryCode") {
        put("type", JsonPrimitive("string"))
    }
    putJsonObject("year") {
        put("type", JsonPrimitive("string"))
    }
},

[John O'Reilly]

(from another one of the Kotlin MCP SDK samples)

[John O'Reilly]

Thanks for the help

[Didier Villevalois]

If you want to be precise, you can do that for `year`:

"date": {
  "type": "string",
  "format": "date"
}

Though it appears this is really not stable yet (https://json-schema.org/draft/2020-12/json-schema-validation#name-dates-times-and-duration)

[John O'Reilly]

yeah, I had used "date" before there but hadn't seemed to work here

[John O'Reilly]

but string seemed to work anyway (it just takes in a year)

[Didier Villevalois]

@John O'Reilly also, if you are writing you MCP server in Kotlin, I really recommend you this: https://github.com/xemantic/xemantic-ai-tool-schema. (there is another similar library in the field but I can't remember its name, but that's something that should IMO be part of kotlinx-serialization...).

You define your @Serializable classes and let it generate the schema...

You can see an examples of its uses here https://github.com/ptitjes/konvo/blob/main/konvo-mcp-web-tools/src/commonMain/kotlin/io/github/ptitjes/konvo/mcp/web/utils/ServerOps.kt#L31, here https://github.com/ptitjes/konvo/blob/main/konvo-mcp-web-tools/src/commonMain/kotlin/io/github/ptitjes/konvo/mcp/web/utils/JsonSchemaOf.kt and here https://github.com/ptitjes/konvo/blob/main/konvo-mcp-web-tools/src/commonMain/kotlin/io/github/ptitjes/konvo/mcp/web/KonvoWebTools.kt#L31

[John O'Reilly]

thanks, will take a look at that

[John O'Reilly]

this is the one I'm currently using https://github.com/modelcontextprotocol/kotlin-sdk

[Didier Villevalois]

@John O'Reilly I am using the same SDK. The library I pointed "just" does the kotlinx-serialization -> JSON schema glue.
You can see in one of the three github excerpts how I use jsonSchemaOf to call the Server.addTool with a simple Kotlin method reference and reified type parameters. All the typing info is already contained in the KSerializer. jsonSchemaOf is using that to produce a JSON schema. Then I simply wrap the Server.addTool call in a inline fun <reified I, reified O> Server.addJsonTool(name: String, description: String, crossinline handler: suspend (I) -> O).

[kaeawc]

I ran into a similar issue and just did some reified types on data classes with kotlin serialization