mountSpec

mountSpec

typescript

mountSpec(router, spec, options?: MountSpecOptions)

Option	Default	Description
basePath	''	Prefix for RPC paths and for paths baked into emitted documents
docs	true	Pass false to disable /docs, /callspec.json, and /openapi.json at the mount root
visibility	'public'	'public' — public-scope routes only. 'all' — also document scope: 'private' routes on this mount (dev/stage). See Auth and scope.
docsPath	'/docs'	Docs UI path on this router (callspec.json and openapi.json paths are fixed)
mcpPath	'/mcp'	MCP HTTP endpoint on this router
logging	true	jsout-express request log on this router + jsout error log on unhandled throws; pass false in tests
onCall	jsout call info when logging	Structured per-call events for MCP tools/call (CallEvent). Custom sink for Logfox; () => {} to disable call events only
handleUnhandledError	—	Catch handler exceptions — see Error handling: mountSpec flow.
logUnhandledError	jsout logger.error when logging is on	Optional (err, req) => void callback; replaces the default unhandled-throw sink

When docs is enabled, the docs UI fetches callspec.json at /callspec.json on this router (fixed path). Override only the UI mount:

typescript

mountSpec(router, spec, {docsPath: '/explorer'});
// UI at /explorer — still loads ../callspec.json relative to that path

Document private routes on this same /docs with visibility: 'all':

typescript

mountSpec(router, spec, {
    visibility: process.env.NODE_ENV === 'production' ? 'public' : 'all',
});

See Error handling: mountSpec flow.

With app.use('/v1', router) and defaults, a server on port 3000 exposes:

Surface	URL
Docs UI	http://127.0.0.1:3000/v1/docs
Contract	http://127.0.0.1:3000/v1/callspec.json
OpenAPI	http://127.0.0.1:3000/v1/openapi.json
RPC	POST http://127.0.0.1:3000/v1/{methodName}
MCP	http://127.0.0.1:3000/v1/mcp (when any route has mcp: true)

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