add webfetch tool use and result formatters

lib/roast/cogs/agent/providers/claude/tool_result.rb

@@ -85,6 +85,30 @@ def format_read
               ok_line("#{count} #{"line".pluralize(count)}")
             end
 
+            # Formats a WebFetch tool-result line.
+            #
+            # Input: :url – the URL that was fetched.
+            # Content: the answer the model produced from the fetched page. A page
+            # that could not be retrieved (e.g. an HTTP 404) still comes back as
+            # a non-error result whose content describes what happened.
+            #
+            # Output: "WEBFETCH OK <url> · <preview>" – the fetched :url followed
+            # by the first line of that answer, stripped and truncated to
+            # TRUNCATE_LIMIT chars. Either part is omitted when absent (no url, or
+            # no content), collapsing to just the other; :url is not truncated, as
+            # it is the identity of the fetch.
+            #
+            # Examples:
+            #   WEBFETCH OK https://example.com · The main heading is "Example Domain".
+            #   WEBFETCH OK https://example.com/missing · The server returned HTTP 404...
+            #   WEBFETCH OK https://example.com
+            #
+            #: () -> String
+            def format_webfetch
+              preview = truncate(content.to_s.lines.first.to_s.strip)
+              ok_line(tool_use_input[:url], preview)
+            end
+
             # Formats a Glob tool-result line.
             #
             # Content: newline-separated matches. Lines starting with "/" are

lib/roast/cogs/agent/providers/claude/tool_use.rb

@@ -108,6 +108,27 @@ def format_read
               details ? "#{label} (#{details})" : label
             end
 
+            # Formats a WebFetch tool-use line.
+            #
+            # Input fields:
+            #   :url    (String) – the URL to fetch                       [required]
+            #   :prompt (String) – what to extract/answer from the page   [required]
+            #
+            # Output: "WEBFETCH <url>", with " (<prompt>)" appended when :prompt is
+            # present. :prompt is truncated to TRUNCATE_LIMIT chars; :url is not, as
+            # it is the identity of the fetch (like a file path in a Read).
+            #
+            # Examples:
+            #   WEBFETCH https://example.com (What is the main heading?)
+            #   WEBFETCH https://example.com
+            #
+            #: () -> String
+            def format_webfetch
+              url, prompt = input.values_at(:url, :prompt)
+              label = url.to_s.empty? ? "WEBFETCH" : "WEBFETCH #{url}"
+              prompt ? "#{label} (#{truncate(prompt)})" : label
+            end
+
             # Formats a Glob tool-use line.
             #
             # Input fields:

test/roast/cogs/agent/providers/claude/tool_result_test.rb

@@ -305,6 +305,87 @@ class Claude::ToolResultTest < ActiveSupport::TestCase
           assert_equal "READ OK 0 lines", output
         end
 
+        test "format_webfetch shows the fetched url and previews the first line of the answer" do
+          tool_use_message = Claude::Messages::ToolUseMessage.new(
+            type: :tool_use,
+            hash: { name: "webfetch", input: { url: "https://example.com", prompt: "What is the main heading?" } },
+          )
+          tool_result = Claude::ToolResult.new(
+            tool_use: tool_use_message,
+            content: "The main heading is \"Example Domain\".\n\nIt appears twice on the page.",
+            is_error: false,
+          )
+
+          output = tool_result.format
+
+          assert_equal "WEBFETCH OK https://example.com · The main heading is \"Example Domain\".", output
+        end
+
+        test "format_webfetch previews a failed fetch that came back as a non-error result" do
+          tool_use_message = Claude::Messages::ToolUseMessage.new(
+            type: :tool_use,
+            hash: { name: "webfetch", input: { url: "https://example.com/missing" } },
+          )
+          tool_result = Claude::ToolResult.new(
+            tool_use: tool_use_message,
+            content: "The server returned HTTP 404 Not Found.\n\nThe response body was not retrieved.",
+            is_error: false,
+          )
+
+          output = tool_result.format
+
+          assert_equal "WEBFETCH OK https://example.com/missing · The server returned HTTP 404 Not Found.", output
+        end
+
+        test "format_webfetch truncates the preview but not the url" do
+          long_url = "https://example.com/#{"a" * (Claude::ToolResult::TRUNCATE_LIMIT + 10)}"
+          tool_use_message = Claude::Messages::ToolUseMessage.new(
+            type: :tool_use,
+            hash: { name: "webfetch", input: { url: long_url } },
+          )
+          tool_result = Claude::ToolResult.new(
+            tool_use: tool_use_message,
+            content: "x" * 60,
+            is_error: false,
+          )
+
+          output = tool_result.format
+
+          assert_equal "WEBFETCH OK #{long_url} · #{"x" * (Claude::ToolResult::TRUNCATE_LIMIT - 3)}...", output
+        end
+
+        test "format_webfetch shows the url alone when the content is nil" do
+          tool_use_message = Claude::Messages::ToolUseMessage.new(
+            type: :tool_use,
+            hash: { name: "webfetch", input: { url: "https://example.com" } },
+          )
+          tool_result = Claude::ToolResult.new(
+            tool_use: tool_use_message,
+            content: nil,
+            is_error: false,
+          )
+
+          output = tool_result.format
+
+          assert_equal "WEBFETCH OK https://example.com", output
+        end
+
+        test "format_webfetch collapses to a bare line when both url and content are absent" do
+          tool_use_message = Claude::Messages::ToolUseMessage.new(
+            type: :tool_use,
+            hash: { name: "webfetch", input: {} },
+          )
+          tool_result = Claude::ToolResult.new(
+            tool_use: tool_use_message,
+            content: "",
+            is_error: false,
+          )
+
+          output = tool_result.format
+
+          assert_equal "WEBFETCH OK", output
+        end
+
         test "format_glob reports the number of matched files" do
           tool_use_message = Claude::Messages::ToolUseMessage.new(
             type: :tool_use,

test/roast/cogs/agent/providers/claude/tool_use_test.rb

@@ -122,6 +122,43 @@ class Claude::ToolUseTest < ActiveSupport::TestCase
           assert_equal "READ", output
         end
 
+        # format_webfetch
+
+        test "format_webfetch appends the prompt in parentheses" do
+          tool_use = Claude::ToolUse.new(name: :webfetch, input: { url: "https://example.com", prompt: "What is the main heading?" })
+
+          output = tool_use.format
+
+          assert_equal "WEBFETCH https://example.com (What is the main heading?)", output
+        end
+
+        test "format_webfetch renders the url only when no prompt given" do
+          tool_use = Claude::ToolUse.new(name: :webfetch, input: { url: "https://example.com" })
+
+          output = tool_use.format
+
+          assert_equal "WEBFETCH https://example.com", output
+        end
+
+        test "format_webfetch truncates the prompt but not the url" do
+          long_url = "https://example.com/#{"a" * (Claude::ToolUse::TRUNCATE_LIMIT + 10)}"
+          long_prompt = "b" * (Claude::ToolUse::TRUNCATE_LIMIT + 10)
+          truncated = "#{"b" * (Claude::ToolUse::TRUNCATE_LIMIT - 3)}..."
+          tool_use = Claude::ToolUse.new(name: :webfetch, input: { url: long_url, prompt: long_prompt })
+
+          output = tool_use.format
+
+          assert_equal "WEBFETCH #{long_url} (#{truncated})", output
+        end
+
+        test "format_webfetch has no trailing space when the url is absent" do
+          tool_use = Claude::ToolUse.new(name: :webfetch, input: {})
+
+          output = tool_use.format
+
+          assert_equal "WEBFETCH", output
+        end
+
         # format_glob
 
         test "format_glob renders the pattern only when no path given" do