diff --git a/claudetool/about_sketch.go b/claudetool/about_sketch.go
new file mode 100644
index 0000000..15a4059
--- /dev/null
+++ b/claudetool/about_sketch.go
@@ -0,0 +1,64 @@
+package claudetool
+
+import (
+	"context"
+	_ "embed"
+	"encoding/json"
+	"fmt"
+	"log/slog"
+	"strings"
+	"text/template"
+
+	"sketch.dev/llm"
+	"sketch.dev/llm/conversation"
+)
+
+// AboutSketch provides information about how to use Sketch.
+var AboutSketch = &llm.Tool{
+	Name:        "about_sketch",
+	Description: aboutSketchDescription,
+	InputSchema: llm.EmptySchema(),
+	Run:         aboutSketchRun,
+}
+
+// TODO: BYO knowledge bases? could do that for strings.Lines, for example.
+// TODO: support Q&A mode instead of reading full text in?
+
+const (
+	aboutSketchDescription = `Provides information about Sketch.
+
+When to use this tool:
+
+- The user is asking how to USE Sketch itself (not asking Sketch to perform a task)
+- The user has questions about Sketch functionality, setup, or capabilities
+- The user needs help with Sketch-specific concepts like running commands, secrets management, git integration
+- The query is about "How do I do X in Sketch?" or "Is it possible to Y in Sketch?" or just "Help"
+- The user is confused about how a Sketch feature works or how to access it
+- You need to know how to interact with the host environment, e.g. port forwarding or pulling changes the user has made outside of Sketch
+`
+)
+
+//go:embed about_sketch.txt
+var aboutSketch string
+
+var aboutSketchTemplate = template.Must(template.New("sketch").Parse(aboutSketch))
+
+func aboutSketchRun(ctx context.Context, m json.RawMessage) ([]llm.Content, error) {
+	slog.InfoContext(ctx, "about_sketch called")
+
+	info := conversation.ToolCallInfoFromContext(ctx)
+	sessionID, _ := info.Convo.ExtraData["session_id"].(string)
+	branch, _ := info.Convo.ExtraData["branch"].(string)
+	dot := struct {
+		SessionID string
+		Branch    string
+	}{
+		SessionID: sessionID,
+		Branch:    branch,
+	}
+	buf := new(strings.Builder)
+	if err := aboutSketchTemplate.Execute(buf, dot); err != nil {
+		return nil, fmt.Errorf("template execution error: %w", err)
+	}
+	return llm.TextContent(buf.String()), nil
+}