diff --git a/src/pages/api/run.ts b/src/pages/api/run.ts
index 2868a11..5ae60c6 100644
--- a/src/pages/api/run.ts
+++ b/src/pages/api/run.ts
@@ -15,6 +15,12 @@ const exec = promisify(execSync)
 
 let tmpDir: string
 
+/**
+ * body is the stl
+ * query
+ * price: algorithm from settings
+ * adionnal settings from https://manual.slic3r.org/advanced/command-line
+ */
 export const post: APIRoute = async ({ request }) => {
 	if (!tmpDir) {
 		tmpDir = await fs.mkdtemp(path.join(os.tmpdir(), 'paas-'))
@@ -121,9 +127,9 @@ export const post: APIRoute = async ({ request }) => {
 	await fs.rm(stlPath)
 	await fs.rm(gcodePath)
 	const params = getParams(gcode)
-	let price = -1
+	let price: string | undefined
 	if (query?.algo) {
-		let algo = query.algo as string
+		let algo = decodeURI(query.algo as string)
 		// objectLoop(params, (value, key) => {
 		// 	if (typeof value !== 'number') {
 		// 		return
@@ -132,13 +138,39 @@ export const post: APIRoute = async ({ request }) => {
 		// 		algo = algo.replace(key, value.toString())
 		// 	}
 		// })
-		price = evaluate(algo, params)
+		try {
+			const tmp = evaluate(algo, params)
+			if (typeof tmp === 'number') {
+				price = tmp.toFixed(2)
+			} else {
+				return buildRFC7807Error({
+					type: '/algorithm-error',
+					status: 500,
+					title: 'Algorithm compilation error',
+					details: 'It seems the algorithm resolution failed',
+					algorithm: algo,
+					algorithmError: 'Algorithm return a Unit',
+					parameters: params
+				})
+			}
+		} catch (e) {
+			console.dir(e)
+			return buildRFC7807Error({
+				type: '/algorithm-error',
+				status: 500,
+				title: 'Algorithm compilation error',
+				details: 'It seems the algorithm resolution failed',
+				algorithm: algo,
+				algorithmError: e,
+				parameters: params
+			})
+		}
 	}
 	console.log('request successfull :)', file)
 	return {
 		status: 200,
 		body: JSON.stringify({
-			price: parseFloat(price.toFixed(2)),
+			price: price ? parseFloat(price) : undefined,
 			...getParams(gcode),
 			gcode
 		})