Stringer Grounded Synthesizer

{'type': 'object', 'required': ['topic'], 'properties': {'depth': {'enum': ['brief', 'deep'], 'type': 'string', 'description': "Research depth: 'brief' ($0.10, >=2 sources) or 'deep' ($0.25, >=3 sources). Default is 'brief'."}, 'topic': {'type': 'string', 'description': 'The topic, entity, or research query to synthesize.'}, 'source_urls': {'type': 'array', 'items': {'type': 'string'}, 'maxItems': 6, 'description': 'Public source URLs supplied by the caller. Brief requires >=2 distinct verified URLs; deep requires >=3.'}, 'domains_filter': {'type': 'array', 'items': {'type': 'string'}, 'description': 'Optional list of domains to filter discovery.'}}}