feat: add input validation for search mode of rag query

docs/_static/llama-stack-spec.html

@@ -14676,7 +14676,8 @@
                         "description": "Template for formatting each retrieved chunk in the context. Available placeholders: {index} (1-based chunk ordinal), {chunk.content} (chunk content string), {metadata} (chunk metadata dict). Default: \"Result {index}\\nContent: {chunk.content}\\nMetadata: {metadata}\\n\""
                     },
                     "mode": {
-                        "type": "string",
+                        "$ref": "#/components/schemas/RAGSearchMode",
+                        "default": "vector",
                         "description": "Search mode for retrieval—either \"vector\", \"keyword\", or \"hybrid\". Default \"vector\"."
                     },
                     "ranker": {
@@ -14711,6 +14712,16 @@
                     }
                 }
             },
+            "RAGSearchMode": {
+                "type": "string",
+                "enum": [
+                    "vector",
+                    "keyword",
+                    "hybrid"
+                ],
+                "title": "RAGSearchMode",
+                "description": "Search modes for RAG query retrieval: - VECTOR: Uses vector similarity search for semantic matching - KEYWORD: Uses keyword-based search for exact matching - HYBRID: Combines both vector and keyword search for better results"
+            },
             "RRFRanker": {
                 "type": "object",
                 "properties": {

docs/_static/llama-stack-spec.yaml

@@ -10260,7 +10260,8 @@ components:
             content string), {metadata} (chunk metadata dict). Default: "Result {index}\nContent:
             {chunk.content}\nMetadata: {metadata}\n"
         mode:
-          type: string
+          $ref: '#/components/schemas/RAGSearchMode'
+          default: vector
           description: >-
             Search mode for retrieval—either "vector", "keyword", or "hybrid". Default
             "vector".
@@ -10287,6 +10288,17 @@ components:
         mapping:
           default: '#/components/schemas/DefaultRAGQueryGeneratorConfig'
           llm: '#/components/schemas/LLMRAGQueryGeneratorConfig'
+    RAGSearchMode:
+      type: string
+      enum:
+        - vector
+        - keyword
+        - hybrid
+      title: RAGSearchMode
+      description: >-
+        Search modes for RAG query retrieval: - VECTOR: Uses vector similarity search
+        for semantic matching - KEYWORD: Uses keyword-based search for exact matching
+        - HYBRID: Combines both vector and keyword search for better results
     RRFRanker:
       type: object
       properties:

llama_stack/apis/tools/rag_tool.py

@@ -87,6 +87,20 @@ class RAGQueryGenerator(Enum):
     custom = "custom"
 
 
+@json_schema_type
+class RAGSearchMode(Enum):
+    """
+    Search modes for RAG query retrieval:
+    - VECTOR: Uses vector similarity search for semantic matching
+    - KEYWORD: Uses keyword-based search for exact matching
+    - HYBRID: Combines both vector and keyword search for better results
+    """
+
+    VECTOR = "vector"
+    KEYWORD = "keyword"
+    HYBRID = "hybrid"
+
+
 @json_schema_type
 class DefaultRAGQueryGeneratorConfig(BaseModel):
     type: Literal["default"] = "default"
@@ -128,7 +142,7 @@ class RAGQueryConfig(BaseModel):
     max_tokens_in_context: int = 4096
     max_chunks: int = 5
     chunk_template: str = "Result {index}\nContent: {chunk.content}\nMetadata: {metadata}\n"
-    mode: str | None = None
+    mode: RAGSearchMode | None = RAGSearchMode.VECTOR
     ranker: Ranker | None = Field(default=None)  # Only used for hybrid mode
 
     @field_validator("chunk_template")