The program fidl_api_summarize extracts FIDL API information from FIDL JSON IR. It wraps the //tools/fidl/lib/summarize library.
fx set core.x64 --with //tools/fidl fx build host-tools/fidl_api_summarize
fx fidl_api_summarize \
--output-file /dev/stdout \
--fidl-ir-file "$(fx get-build-dir)/fidling/gen/sdk/fidl/fuchsia.net/fuchsia.net.fidl.json"