Allow @Schema on Tool requests and read description from annotations when available

core/src/commonMain/kotlin/com/xebia/functional/xef/conversation/Schema.kt

@@ -0,0 +1,11 @@
+package com.xebia.functional.xef.conversation
+
+import kotlinx.serialization.ExperimentalSerializationApi
+import kotlinx.serialization.SerialInfo
+
+/** Schema for a tool request */
+@OptIn(ExperimentalSerializationApi::class)
+@SerialInfo
+@Retention(AnnotationRetention.RUNTIME)
+@Target(AnnotationTarget.CLASS)
+annotation class Schema(val value: String)

core/src/commonMain/kotlin/com/xebia/functional/xef/llm/ChatWithFunctions.kt

@@ -7,9 +7,12 @@ import com.xebia.functional.openai.generated.api.Chat
 import com.xebia.functional.openai.generated.model.*
 import com.xebia.functional.xef.AIError
 import com.xebia.functional.xef.AIEvent
+import com.xebia.functional.xef.Config
 import com.xebia.functional.xef.Tool
 import com.xebia.functional.xef.conversation.AiDsl
 import com.xebia.functional.xef.conversation.Conversation
+import com.xebia.functional.xef.conversation.Description
+import com.xebia.functional.xef.conversation.Schema
 import com.xebia.functional.xef.llm.models.functions.buildJsonSchema
 import com.xebia.functional.xef.prompt.Prompt
 import com.xebia.functional.xef.prompt.PromptBuilder.Companion.tool
@@ -21,17 +24,31 @@ import kotlinx.serialization.ExperimentalSerializationApi
 import kotlinx.serialization.descriptors.SerialDescriptor
 import kotlinx.serialization.json.*
 
-@OptIn(ExperimentalSerializationApi::class)
 fun chatFunction(descriptor: SerialDescriptor): FunctionObject {
-  val fnName = descriptor.serialName.substringAfterLast(".")
-  return chatFunction(fnName, buildJsonSchema(descriptor))
+  val functionName = functionName(descriptor)
+  return FunctionObject(
+    name = functionName,
+    description = functionDescription(descriptor, functionName),
+    parameters = functionSchema(descriptor)
+  )
 }
 
-fun chatFunctions(descriptors: List<SerialDescriptor>): List<FunctionObject> =
-  descriptors.map(::chatFunction)
+@OptIn(ExperimentalSerializationApi::class)
+fun functionSchema(descriptor: SerialDescriptor): JsonObject =
+  descriptor.annotations.filterIsInstance<Schema>().firstOrNull()?.value?.let {
+    Config.DEFAULT.json.decodeFromString(JsonObject.serializer(), it)
+  } ?: buildJsonSchema(descriptor)
 
-fun chatFunction(fnName: String, schema: JsonObject): FunctionObject =
-  FunctionObject(fnName, "Generated function for $fnName", schema)
+@OptIn(ExperimentalSerializationApi::class)
+fun functionDescription(descriptor: SerialDescriptor, fnName: String): String =
+  (descriptor.annotations.filterIsInstance<Description>().firstOrNull()?.value
+    ?: defaultFunctionDescription(fnName))
+
+fun defaultFunctionDescription(fnName: String): String = "Generated function for $fnName"
+
+@OptIn(ExperimentalSerializationApi::class)
+fun functionName(descriptor: SerialDescriptor): String =
+  descriptor.serialName.substringAfterLast(".")
 
 data class UsageTracker(
   var llmCalls: Int = 0,

core/src/commonTest/kotlin/com/xebia/functional/xef/functions/FunctionSchemaTests.kt

@@ -0,0 +1,55 @@
+package com.xebia.functional.xef.functions
+
+import com.xebia.functional.xef.conversation.Description
+import com.xebia.functional.xef.conversation.Schema
+import com.xebia.functional.xef.llm.chatFunction
+import com.xebia.functional.xef.llm.defaultFunctionDescription
+import com.xebia.functional.xef.llm.functionName
+import com.xebia.functional.xef.llm.models.functions.buildJsonSchema
+import io.kotest.core.spec.style.StringSpec
+import io.kotest.matchers.shouldBe
+import kotlinx.serialization.Serializable
+import kotlinx.serialization.json.JsonObject
+
+class FunctionSchemaTests :
+  StringSpec({
+    "Request has default description" {
+      val descriptor = Request.serializer().descriptor
+      val function = chatFunction(descriptor)
+      val fnName = functionName(descriptor)
+      function.description shouldBe defaultFunctionDescription(fnName)
+    }
+
+    "Description can be set on request" {
+      val descriptor = RequestWithDescription.serializer().descriptor
+      val function = chatFunction(descriptor)
+      function.description shouldBe "Request With Description"
+    }
+
+    "Schema can be generated on request" {
+      val descriptor = Request.serializer().descriptor
+      val function = chatFunction(descriptor)
+      function.parameters shouldBe buildJsonSchema(descriptor)
+    }
+
+    "Schema can be set on request" {
+      val descriptor = RequestWithSchema.serializer().descriptor
+      val function = chatFunction(descriptor)
+      function.parameters shouldBe JsonObject(emptyMap())
+    }
+  }) {
+
+  @Serializable data class Request(val input: String)
+
+  @Serializable
+  @Description("Request With Description")
+  data class RequestWithDescription(val input: String)
+
+  @Serializable
+  @Description("Request with schema")
+  @Schema("""
+    {
+    }
+  """)
+  data class RequestWithSchema(val input: String)
+}