bxcore, brokerd, loopd: an invalid-arguments denial says why

Co-Authored-By: ornith-1.5-35b-a3b <agent@wntrmute.dev>

crates/loopd/src/tools.rs

@@ -378,6 +378,19 @@ pub fn denial_text(reason: bxcore::DenyReason) -> &'static str {
     }
 }
 
+/// What a denial reaches the model as: the reason's sentence, and the broker's detail, if it sent
+/// one, after a colon (`Denied: the arguments are not valid for this tool: <detail>.`).
+pub fn denial_message(reason: bxcore::DenyReason, detail: Option<&str>) -> String {
+    let sentence = denial_text(reason);
+    match detail {
+        None => sentence.to_string(),
+        Some(detail) => {
+            let stem = sentence.strip_suffix('.').unwrap_or(sentence);
+            format!("{stem}: {detail}.")
+        }
+    }
+}
+
 pub struct FakeTools {
     calls: Mutex<Vec<bxcore::ToolRequest>>,
 }
@@ -432,6 +445,7 @@ impl ToolPort for FakeTools {
             },
             _ => bxcore::ToolResponse::Denied {
                 reason: bxcore::DenyReason::NoGrant,
+                detail: None,
             },
         }
     }

crates/loopd/src/turn.rs

@@ -7,7 +7,7 @@ use crate::config::Config;
 use crate::llama::info::{CacheOutcome, cache_outcome};
 use crate::llama::{ChatEvent, ChatRequest, Client, InferError};
 use crate::session::{Session, SessionError};
-use crate::tools::{Registry, ToolPort, cap_result, denial_text, dispatch};
+use crate::tools::{Registry, ToolPort, cap_result, denial_message, dispatch};
 use bxcore::{
     CallId, DataClass, LogRecord, Timestamp, ToolRequest, ToolResponse, TurnEvent, Usage,
 };
@@ -292,12 +292,16 @@ fn run_call(
                     DataClass::Public,
                     false,
                 ),
-                ToolResponse::Denied { reason } => {
+                ToolResponse::Denied { reason, detail } => {
                     on_event(&TurnEvent::ToolDenied {
                         name: request.tool.clone(),
                         reason,
                     });
-                    (denial_text(reason).to_string(), DataClass::Public, false)
+                    (
+                        denial_message(reason, detail.as_deref()),
+                        DataClass::Public,
+                        false,
+                    )
                 }
                 ToolResponse::PendingApproval { .. } => (
                     "The tool failed: the tool broker gave no final answer".to_string(),