mcp: the probe tool takes at, points whose nearest nodes are probed (#105)

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01UhhZMBTviDQxZvwnyP89fo

crates/mcp/src/tests.rs

@@ -224,6 +224,22 @@ fn screenshot_takes_a_camera_orientation() {
     assert_eq!(again, turned);
 }
 
+/// `probe {at}` reads a structural result at the nodes nearest to points (#105); hostile points
+/// are refused without a panic.
+#[test]
+fn probe_takes_points_at() {
+    let mut s = server();
+    ok(&mut s, "execute", json!({"command": "file.sample", "params": {"name": "cantilever"}}));
+    ok(&mut s, "solve", json!({"analysis": "static", "step": "Load"}));
+    let r = ok(&mut s, "probe", json!({"step": "Load", "at": [[0, 0, 0]]}));
+    let node = &r["nodes"][0];
+    assert!(node["xyz"].is_array() && node["distance"].is_number(), "{r}");
+    for at in [json!([[1e308, "x"]]), json!(vec![json!([0, 0, 0]); 20_000])] {
+        let (text, err) = call(&mut s, "probe", json!({"step": "Load", "at": at}));
+        assert!(err && text.len() < 100_000, "{text}");
+    }
+}
+
 #[test]
 fn a_batch_stops_at_the_first_error() {
     let mut s = server();

crates/mcp/src/tools.rs

@@ -251,7 +251,7 @@ pub fn tool_definitions() -> Vec<Value> {
         tool(
             "probe",
             "Probe results",
-            "Stored results at nodes (solve.probe): displacement, reaction, stress and von Mises (static), the shape of \
+            "Stored results at nodes, or at the nodes nearest to points `at` (solve.probe): displacement, reaction, stress and von Mises (static), the shape of \
              mode `mode` (frequency), displacement and velocity in field frame `frame` (explicit) and, with `elements`, \
              explicit element values; for a fluid step, the flow at `points` and the force histories of `forces`.",
             obj(
@@ -259,6 +259,7 @@ pub fn tool_definitions() -> Vec<Value> {
                     "step": string("Solved step"),
                     "nodes": {"type": "array", "items": {"type": "integer"}, "description": "Node labels"},
                     "elements": {"type": "array", "items": {"type": "integer"}, "description": "Element labels (explicit)"},
+                    "at": {"type": "array", "items": {"type": "array"}, "description": "Points [x, y, z]; the nearest nodes are probed (structural steps)"},
                     "points": {"type": "array", "items": {"type": "array"}, "description": "Points [x, y, z] (fluid)"},
                     "forces": {"type": "array", "items": {"type": "string"}, "description": "Walls or faces whose force histories to return (fluid)"},
                     "mode": integer("Mode, from 1 (frequency)"),
@@ -497,7 +498,7 @@ fn dispatch(b: &mut dyn Backend, name: &str, a: &Map<String, Value>) -> Result<V
             b.execute(command, params)
         }
         "show_results" => show_results(b, a),
-        "probe" => b.execute("solve.probe", pick(a, &["step", "nodes", "elements", "points", "forces", "mode", "frame"])),
+        "probe" => b.execute("solve.probe", pick(a, &["step", "nodes", "at", "elements", "points", "forces", "mode", "frame"])),
         "reactions" => b.execute("results.reactions", pick(a, &["step", "sets", "about"])),
         "select" => {
             let p = pick(a, &["filter", "box_mode", "mode", "clear", "geometry", "nodes", "elements", "faces", "at", "box"]);