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mcp_faq

MCP FAQ​

What is Loopback MCP?​

An in‑process MCP server inside CRUDService that exposes tools derived from your ServiceConfigs and serves them via REST and JSON‑RPC.

How do I list tools?​

Use GET /mcp/tools/list or JSON‑RPC tools/list via /mcp/jsonrpc (or the BFF proxy routes).

How do I invoke tools?​

Use JSON‑RPC tools/invoke or tools/call with { name, arguments }.

Why two health names?​

system.health and system_health are both provided for client compatibility.

Why namespaced names?​

Different providers/instances require different schemas. Namespaced provider.instance.base avoids collisions and ambiguity; workflows use workflow.<name>.

Can workflows run immediately?​

By default they validate inputs and return an accepted stub. To start immediately in dev/test, set MCP_LOOPBACK_WORKFLOW_DIRECT_INVOKE=true in CRUDService.

I get 403 errors​

Your token is missing required scopes (mcp.tools.discovery for list, mcp.tools.invoke for invoke), or BFF session/auth is failing.

The tool catalogue is empty​

Confirm ServiceConfigs are mounted and valid; the ToolCatalogue refreshes after config mutations. Check MCP_MAX_TOOLS cap.

My tool name is too long​

Names are capped (≤50 for generation, ≤64 in catalogue). Over‑long names are compacted with a stable hash; the catalogue skips names >64.