Improved the errors models get from web search for invalid arguments

app/Tests/Tools/ToolCalling/WebSearchToolArgumentTests.cs

@@ -0,0 +1,157 @@
+using System.Text.Json;
+
+using AIStudio.Tools.ToolCallingSystem.ToolCallingImplementations.WebSearch;
+
+namespace AIStudio.Tests.Tools.ToolCalling;
+
+/// <summary>
+/// Checks how the web search reads the arguments a model passes, and what it says about wrong ones.
+/// </summary>
+/// <remarks>
+/// A wrong argument is refused rather than guessed at: a placeholder such as 0 is not a page, and
+/// quietly reading it as "no page" would do something the model did not ask for. What makes the
+/// refusal work is its message. The model reads it and tries again, so it has to say what arrived,
+/// what would have been right, and that an optional argument may simply be left out. A model
+/// which believes it has to pass one otherwise keeps trying placeholders, and every attempt costs
+/// one of the tool calls an answer may make.
+/// </remarks>
+[TestFixture]
+public sealed class WebSearchToolArgumentTests
+{
+    [Test]
+    public void AnArgumentLeftOutIsNotSet()
+    {
+        var arguments = Arguments("""{"query":"weather"}""");
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(WebSearchTool.ReadLanguage(arguments), Is.Null);
+            Assert.That(WebSearchTool.ReadTimeRange(arguments), Is.Null);
+            Assert.That(WebSearchTool.ReadPage(arguments), Is.Null);
+            Assert.That(WebSearchTool.ReadLimit(arguments), Is.Null);
+        });
+    }
+
+    [Test]
+    public void ANullArgumentIsTheSameAsOneLeftOut()
+    {
+        var arguments = Arguments("""{"query":"weather","language":null,"time_range":null,"page":null,"limit":null}""");
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(WebSearchTool.ReadLanguage(arguments), Is.Null);
+            Assert.That(WebSearchTool.ReadTimeRange(arguments), Is.Null);
+            Assert.That(WebSearchTool.ReadPage(arguments), Is.Null);
+            Assert.That(WebSearchTool.ReadLimit(arguments), Is.Null);
+        });
+    }
+
+    [Test]
+    public void ValidArgumentsComeThrough()
+    {
+        var arguments = Arguments("""{"query":"  weather  ","language":"de-DE","time_range":"day","page":2,"limit":7}""");
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(WebSearchTool.ReadQuery(arguments), Is.EqualTo("weather"));
+            Assert.That(WebSearchTool.ReadLanguage(arguments), Is.EqualTo("de-DE"));
+            Assert.That(WebSearchTool.ReadTimeRange(arguments), Is.EqualTo("day"));
+            Assert.That(WebSearchTool.ReadPage(arguments), Is.EqualTo(2));
+            Assert.That(WebSearchTool.ReadLimit(arguments), Is.EqualTo(7));
+        });
+    }
+
+    [TestCase("0")]
+    [TestCase("-1")]
+    [TestCase("2.5")]
+    [TestCase("\"5\"")]
+    [TestCase("true")]
+    public void AWrongPageIsRefusedWithWhatArrived(string value)
+    {
+        var message = Refusal(() => WebSearchTool.ReadPage(Arguments($$"""{"query":"weather","page":{{value}}}""")));
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(message, Does.Contain("'page'").And.Contain("a positive integer"));
+            Assert.That(message, Does.Contain($"but was {value}."), "Without the value, the model cannot tell which of its arguments the tool means.");
+            Assert.That(message, Does.Contain("Leave it out"), "The way out a model needs when it believes the argument is required.");
+        });
+    }
+
+    [TestCase("0")]
+    [TestCase("-1")]
+    [TestCase("\"5\"")]
+    public void AWrongLimitIsRefusedWithWhatArrived(string value)
+    {
+        var message = Refusal(() => WebSearchTool.ReadLimit(Arguments($$"""{"query":"weather","limit":{{value}}}""")));
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(message, Does.Contain("'limit'").And.Contain("a positive integer"));
+            Assert.That(message, Does.Contain($"but was {value}."));
+            Assert.That(message, Does.Contain("Leave it out"));
+        });
+    }
+
+    [TestCase("\"\"")]
+    [TestCase("\"Day\"")]
+    [TestCase("\"week\"")]
+    [TestCase("5")]
+    public void AWrongTimeRangeIsRefusedWithTheValuesThatWouldDo(string value)
+    {
+        var message = Refusal(() => WebSearchTool.ReadTimeRange(Arguments($$"""{"query":"weather","time_range":{{value}}}""")));
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(message, Does.Contain("'time_range'").And.Contain("one of day, month, year"));
+            Assert.That(message, Does.Contain($"but was {value}."));
+            Assert.That(message, Does.Contain("Leave it out"));
+        });
+    }
+
+    [Test]
+    public void ALanguageWhichIsNoStringIsRefused()
+    {
+        var message = Refusal(() => WebSearchTool.ReadLanguage(Arguments("""{"query":"weather","language":5}""")));
+        Assert.That(message, Does.Contain("'language'").And.Contain("but was 5.").And.Contain("Leave it out"));
+    }
+
+    [Test]
+    public void AMissingQueryIsRefused()
+    {
+        var message = Refusal(() => WebSearchTool.ReadQuery(Arguments("""{"page":1}""")));
+        Assert.That(message, Does.Contain("Missing required argument 'query'"));
+    }
+
+    [Test]
+    public void AQueryWhichIsNoStringIsRefusedWithoutOfferingToLeaveItOut()
+    {
+        var message = Refusal(() => WebSearchTool.ReadQuery(Arguments("""{"query":42}""")));
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(message, Does.Contain("'query'").And.Contain("but was 42."));
+            Assert.That(message, Does.Not.Contain("Leave it out"), "The query is required, so leaving it out is no way out.");
+        });
+    }
+
+    [Test]
+    public void ALongValueIsShortenedInTheMessage()
+    {
+        var longValue = new string('x', 500);
+        var message = Refusal(() => WebSearchTool.ReadTimeRange(Arguments($$"""{"query":"weather","time_range":"{{longValue}}"}""")));
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(message, Does.Not.Contain(longValue), "The model sent the value itself; repeating all of it back only costs tokens.");
+            Assert.That(message, Does.Contain("..."));
+        });
+    }
+
+    private static JsonElement Arguments(string json) => JsonSerializer.Deserialize<JsonElement>(json);
+
+    /// <summary>
+    /// Runs a reader which has to refuse its argument and returns what it said.
+    /// </summary>
+    private static string Refusal(TestDelegate read) => Assert.Throws<ArgumentException>(read)!.Message;
+}