diff --git a/package.json5 b/package.json5
index 5ede49d..12d0a32 100644
--- a/package.json5
+++ b/package.json5
@@ -4,7 +4,8 @@
    description: 'Another prototype for a math core',
    scripts: {
       build: 'tsc && cp etc/package.json build/',
-      go: 'pnpm build && pnpm start',
+      reflect: 'node tools/reflectTypes.mjs',
+      go: 'pnpm build && pnpm reflect &&  pnpm start',
       start: 'node --experimental-loader tsc-module-loader build',
       test: 'echo Error no test specified && exit 1',
    },
diff --git a/src/core/Dispatcher.ts b/src/core/Dispatcher.ts
index 69b90ee..5b4bd1d 100644
--- a/src/core/Dispatcher.ts
+++ b/src/core/Dispatcher.ts
@@ -135,7 +135,7 @@ interface ImplementationBuilder<
       Specs & {[K in NewKeys]: DepCheck<RD, Signatures>}
    >
 
-   ship(): Implementations<Signatures, NeedKeys, NeedList, Specs>
+   ship(): Implementations<Signatures, NeedKeys, NeedList, Specs> & { reflectedType5: string }
 }
 
 // And a function that actually provides the builder interface:
@@ -189,7 +189,7 @@ function impBuilder<
       },
       ship() {
          return (sofar as
-            Implementations<Signatures, NeedKeys, NeedList, Specs>)
+            Implementations<Signatures, NeedKeys, NeedList, Specs> & { reflectedType5: string })
       }
    }
 }
diff --git a/tools/reflectTypes.mjs b/tools/reflectTypes.mjs
new file mode 100644
index 0000000..4ffa0ad
--- /dev/null
+++ b/tools/reflectTypes.mjs
@@ -0,0 +1,58 @@
+import { readFileSync, writeFileSync, readdirSync } from 'node:fs'
+import { fileURLToPath } from 'node:url'
+import { dirname, join, relative } from 'node:path'
+
+const __filename = fileURLToPath(import.meta.url)
+const __dirname = dirname(__filename)
+
+const buildDir = join(__dirname, '..', 'build')
+const files = (await readdirSync(buildDir, { recursive: true }))
+  .filter(file => file.endsWith('.js'))
+  .map(file => join(buildDir, file))
+
+for (const file of files) {
+  reflectType(file, { debug: true })
+}
+
+function reflectType(srcFile, options = { debug: false }) {
+  log(`Reflecting file "${relative(__dirname, srcFile)}"`)
+
+  const defFile = srcFile.replace(/.js$/, '.d.ts')
+  const src = String(readFileSync(srcFile))
+  const defs = String(readFileSync(defFile))
+
+  if (src.includes('.reflectedType5')) {
+    log('  Source file already contains reflected types and will be ignored')
+    return
+  }
+
+  const matches = Array.from(src.matchAll(/[^\n](export +)?const +([\w$]+) += +implementations\b/g))
+
+  if (matches.length === 0) {
+    log(`  No implementations found`)
+    return
+  }
+
+  for (const match of matches) {
+    const name = match[2]
+    log(`  Found an implementations definition: "${name}"`)
+
+    const def = new RegExp(`export declare const ${name}: {(?:(?!\n}).)+\n}`, 's').exec(defs)
+
+    if (def) {
+      log(`  Injected type definitions for "${name}"`)
+
+      const srcReflected = `${src}\n${name}.reflectedType5 = \`${def}\`\n`
+
+      writeFileSync(srcFile, srcReflected)
+    } else {
+      log(`  No type definitions found for "${name}"`)
+    }
+  }
+
+  function log(...args) {
+    if (options.debug) {
+      console.log(...args)
+    }
+  }
+}