1 files changed, 57 insertions, 0 deletions
diff --git a/src/ping_tool.zig b/src/ping_tool.zig
new file mode 100644
index 0000000..eb212af
--- /dev/null
+++ b/src/ping_tool.zig
@@ -0,0 +1,57 @@
+//! A trivial built-in "ping" tool used to exercise the tool-call loop
+//! end-to-end against a real LLM. It accepts a `host` string and always
+//! returns the literal string "PONG", regardless of what the host is.
+//!
+//! In phase 5 this kind of built-in will be replaced by a proper extension;
+//! for now it lives in the CLI so we can verify the libpanto tool plumbing
+//! without writing the Lua bridge first.
+
+const std = @import("std");
+const panto = @import("panto");
+
+const NAME = "ping";
+const DESCRIPTION =
+    \\Test whether a server is reachable by hostname. Always responds with
+    \\"PONG" when the server is up. Use this when the user asks you to check
+    \\if a host is online or reachable.
+;
+const SCHEMA_JSON =
+    \\{
+    \\  "type": "object",
+    \\  "properties": {
+    \\    "host": {
+    \\      "type": "string",
+    \\      "description": "The hostname or address to ping."
+    \\    }
+    \\  },
+    \\  "required": ["host"]
+    \\}
+;
+
+/// Returns a `Tool` value ready to register with `Agent.registerTool`. The
+/// tool holds no per-instance state: name, description, and schema are
+/// `comptime` string literals, and the vtable's deinit is a no-op. We pass
+/// a sentinel pointer as ctx since the contract requires *anyopaque but
+/// nothing dereferences it.
+pub fn tool() panto.Tool {
+    return .{
+        .name = NAME,
+        .description = DESCRIPTION,
+        .schema_json = SCHEMA_JSON,
+        .ctx = &ctx_sentinel,
+        .vtable = &vtable,
+    };
+}
+
+var ctx_sentinel: u8 = 0;
+
+const vtable: panto.Tool.VTable = .{
+    .invoke = invoke,
+    .deinit = deinitNoop,
+};
+
+fn invoke(_: *anyopaque, _: []const u8, allocator: std.mem.Allocator) anyerror![]u8 {
+    return try allocator.dupe(u8, "PONG");
+}
+
+fn deinitNoop(_: *anyopaque, _: std.mem.Allocator) void {}