virtuoso_mcp

Virtuoso MCP Server

MCP server for Virtuoso Community Edition with guardrailed SPARQL tools and optional domain plugins.

Current transport

• FastMCP (SSE) mounted at GET /mcp/sse
• message endpoint provided by FastMCP under /mcp/messages/
• legacy compatibility router at POST /rpc ({"tool":"...","input":{...}})
• health/discovery at GET / and GET /health

Why this shape

• mcporter compatibility via FastMCP transport
• stable migration path for existing internal scripts via /rpc

Run

pip install -r requirements.txt
./run.sh

Default host/port: 0.0.0.0:8501

Core tools

• Query/navigation: sparql_query, list_graphs, search_label, get_entities_by_type, get_predicates_for_subject, get_labels_for_subject, traverse_property
• Ontology discovery: list_classes, list_properties, describe_class, describe_property
• Relationship helpers: describe_subject, path_traverse, property_usage_statistics
• Update helpers: insert_triple, batch_insert, load_examples

Domain plugin tools (garden layer)

Current garden-prefixed set is intentionally trimmed to non-redundant domain helpers:

• garden_add_seedling
• garden_cycle_plants
• garden_latest_cycle_by_dates
• garden_clone_to
• garden_cycle_list_detailed
• garden_reassign_cycle

Guardrails

• sparql_query is SELECT-only
• LIMIT is enforced (SPARQL_DEFAULT_LIMIT, clamped by SPARQL_MAX_LIMIT)
• fixture loading requires MCP_ALLOW_EXAMPLE_LOAD=true

Environment

Use .env (optional). Key variables:

• VIRTUOSO_ENDPOINT, VIRTUOSO_USER, VIRTUOSO_PASS
• SPARQL_TIMEOUT, SPARQL_UPDATE_TIMEOUT
• SPARQL_DEFAULT_LIMIT, SPARQL_MAX_LIMIT
• GRAPH_URI, EXAMPLE_GRAPH
• MCP_ALLOW_EXAMPLE_LOAD
• DOMAIN_LAYERS (default: garden_layer.plugin)

Tests

./test.sh

(Exercises /rpc compatibility flow and validates guardrailed behavior.)