From c3951a448c022add2e159929ce60d1c9b5641c2c Mon Sep 17 00:00:00 2001
From: kevin9327 <kevin9327@users.noreply.github.com>
Date: Fri, 4 Sep 2026 20:12:02 +0900
Subject: [PATCH] fix(tools): report the ListMcpResources cap in resources, not
 bytes

`gate_mcp_resources` caps the list at `MCP_RESOURCE_LIMIT` (200 resources),
then describes that truncation with `truncation_notice`, which is written
for byte budgets and was handed `MCP_TEXT_LIMIT`. A server returning 250
resources produced:

    [truncated: ListMcpResources result exceeded 32768 bytes; showing 200 of 250 bytes]

Neither figure describes what happened: 32768 is a text budget this path
never applies, and the counts are resources rather than bytes. The notice
goes into a sentinel resource's description, so it is what the model reads
to learn why the list is short -- and it invites the conclusion that the
list was cut for size and would fit under a smaller byte budget.

State the cap that was actually applied, in its own unit, matching the
wording the sibling item-count truncation in `gate_mcp` already uses.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
---
 .../src/cursor/tools/tool_call_result/gate.rs | 43 ++++++++++++++++---
 1 file changed, 38 insertions(+), 5 deletions(-)

diff --git a/server/src/cursor/tools/tool_call_result/gate.rs b/server/src/cursor/tools/tool_call_result/gate.rs
index 3c72a4b..b12283a 100644
--- a/server/src/cursor/tools/tool_call_result/gate.rs
+++ b/server/src/cursor/tools/tool_call_result/gate.rs
@@ -517,11 +517,9 @@ fn gate_mcp_resources(tool: &mut pb::ListMcpResourcesToolCall) {
             .push(pb::list_mcp_resources_exec_result::McpResource {
                 uri: "truncated:list-mcp-resources".into(),
                 name: Some("truncated".into()),
-                description: Some(truncation_notice(
-                    "ListMcpResources",
-                    MCP_TEXT_LIMIT,
-                    success.resources.len(),
-                    original,
+                description: Some(format!(
+                    "[truncated: ListMcpResources result exceeded {MCP_RESOURCE_LIMIT} resources; showing {} of {original} resources]",
+                    success.resources.len()
                 )),
                 ..Default::default()
             });
@@ -861,4 +859,39 @@ mod tests {
         let mut content = String::new();
         tool_completion("Grep", &mut tool, &mut content);
     }
+
+    #[test]
+    fn list_mcp_resources_reports_the_cap_it_actually_applied() {
+        let resources = (0..MCP_RESOURCE_LIMIT + 50)
+            .map(|index| pb::list_mcp_resources_exec_result::McpResource {
+                uri: format!("mcp://resource/{index}"),
+                ..Default::default()
+            })
+            .collect();
+        let mut tool = pb::ListMcpResourcesToolCall {
+            args: None,
+            result: Some(pb::ListMcpResourcesExecResult {
+                result: Some(pb::list_mcp_resources_exec_result::Result::Success(
+                    pb::ListMcpResourcesSuccess { resources },
+                )),
+            }),
+        };
+
+        gate_mcp_resources(&mut tool);
+
+        let pb::list_mcp_resources_exec_result::Result::Success(success) =
+            tool.result.unwrap().result.unwrap()
+        else {
+            panic!("expected a successful result");
+        };
+        let notice = success.resources.last().unwrap();
+        assert_eq!(notice.uri, "truncated:list-mcp-resources");
+        assert_eq!(
+            notice.description.as_deref(),
+            Some(
+                "[truncated: ListMcpResources result exceeded 200 resources; \
+                 showing 200 of 250 resources]"
+            )
+        );
+    }
 }