get_dataset_schema tool to return compact TSV response

Author: nikhilsinhaparseable

src/handlers/http/logstream.rs

@@ -205,7 +205,9 @@ fn schema_response(schema: &Schema, format: SchemaFormat) -> HttpResponse {
     }
 }
 
-fn compact_schema(schema: &Schema) -> String {
+/// Render the token-efficient schema representation used by the compact HTTP
+/// response and by agent-facing schema tools.
+pub fn compact_schema(schema: &Schema) -> String {
     let mut output = String::from("name\ttype\n");
     for field in schema.fields() {
         append_escaped_compact_field(&mut output, field.name());

src/tool_catalog.rs

@@ -356,7 +356,7 @@ pub fn oss_read_tool_specs() -> Vec<ToolSpec> {
         ToolSpec::new(
             "get_dataset_schema",
             "Get dataset schema",
-            "Get columns and data types for a dataset.",
+            "Get all dataset columns and data types as compact tab-separated text with a name/type header.",
             dataset_schema(),
         ),
         ToolSpec::new(

src/tool_executor.rs

@@ -272,12 +272,10 @@ async fn execute_dataset_metadata_tool(
     match name {
         "get_dataset_schema" => {
             authorize(context.session_key, Action::GetSchema, Some(dataset), None)?;
-            serde_json::to_value(
-                logstream::get_schema_internal(dataset, context.tenant_id)
-                    .await
-                    .map_err(|error| error.to_string())?,
-            )
-            .map_err(|error| error.to_string())
+            let schema = logstream::get_schema_internal(dataset, context.tenant_id)
+                .await
+                .map_err(|error| error.to_string())?;
+            Ok(Value::String(logstream::compact_schema(&schema)))
         }
         "get_dataset_info" => {
             authorize(