0004 An agent must have a forced (and hidden) rag_search index

Status

Accepted

Context

ai_search:rag_search is a normal agent tool: by default the LLM can choose which index to query at call time. Retrieval for answers, however, must always target a known, administrator-approved index.

Decision

RagSettingsResolver reads only tool_usage_limits['ai_search:rag_search']['index']['values'][0]. If that value is missing, AnswerService::answer() throws a DomainException and the agent is refused for use with answers.

Consequences

• An LLM-pickable index means prompt injection in the conversation could redirect retrieval at an index the operator never intended to expose. Forcing the value and hiding the property removes index from the model's tool schema entirely, so it is not just discouraged but unreachable.
• Configuring an agent for answers always requires the extra force-value-and-hide step documented in Getting started.