Build the critcl wrapper for Tcl_ParseCommand using make:

% make

This creates the wrapper as a package in directory lib.

Start lsp.tcl from emacs:

(with-eval-after-load 'lsp-mode
  (add-to-list 'lsp-language-id-configuration
               '(tcl-mode . "tcl"))

  (lsp-register-client
   (make-lsp-client :new-connection (lsp-stdio-connection "/home/josd/Development/src/lsp/lsp.tcl")
                    :activation-fn (lsp-activate-on "tcl")
                    :server-id 'lsptcl)))

Now load a Tcl file and load lsp.