One solution to integrating Schema and Datomic

datomic-schema.clj

(in-ns test
   (:require
     [schema.macros :as macros] 
     [schema.utils :as sutils]))

;; Wrapper type needed because Entity values do not implement
;; IPersistentMap interface
(defrecord EntitySchema 
  [schema]
  Schema
  (walker [this]
    (let [map-checker (s/subschema-walker schema)]
      (fn [e]
        (or (when-not (sd/entity? e)
              (macros/validation-error this e 
                (list 'instance? datomic.Entity (sutils/value-name e))))
            (map-checker (into {} (seq e)))))))
  (explain [this]
    (list 'entity 'datomic.Entity (explain (:schema this)))))

(defn entity-schema? 
  [schema]
  (= (type schema) EntitySchema))

(defn model-base-schema 
  "Generates a schema for Datomic entity with model tag 'type'"
  [type]
  {:pre [(keyword? type)]}
  (EntitySchema. {:model/id s/Uuid
                  :model/type (s/both s/Keyword (s/eq type))}))

As sd/entity? is not defined you can use (instance? datomic.Entity e) in its place.