feat: initialize agents from a2a template

agent_builder/builder.py

@@ -84,6 +84,11 @@ when you deploy through the control plane).
 
 Your tools:
 
+  - init_agent_template(name, description)
+                                  — initialize agents/<name>/ from the
+                                    installed a2a-pack `a2a init` template.
+                                    Use this FIRST for a new project, then
+                                    edit the generated files.
   - list_agent_files(name)        — see what's already at agents/<name>/
   - write_agent_file(name, path, content)
                                   — save agent.py / a2a.yaml / requirements.txt
@@ -116,8 +121,10 @@ Discipline:
 
   - Pick a kebab-case slug for ``name`` (e.g. ``research-agent``,
     ``csv-sanitizer``). Class name is PascalCase from the slug.
-  - Write ALL THREE files (agent.py, a2a.yaml, requirements.txt) before
-    testing — partial scaffolds break ``a2a card``.
+  - For a new project, call init_agent_template first. Then read/edit the
+    generated files instead of inventing boilerplate from memory.
+  - Ensure all three core files (agent.py, a2a.yaml, requirements.txt)
+    exist before testing — partial scaffolds break ``a2a card``.
   - Always run test_agent_in_sandbox before deploying. If exit_code != 0,
     read stderr, edit the offending file, retest. Do NOT deploy a broken
     scaffold.

agent_builder/tools.py

@@ -14,6 +14,7 @@ import re
 import tarfile
 import time
 from dataclasses import dataclass
+from importlib import resources
 from typing import TYPE_CHECKING, Any
 
 import boto3
@@ -111,6 +112,36 @@ def build_tools(ctx: ToolContext) -> list[Any]:
     s3 = _s3(ctx)
     _ensure_bucket(s3, bucket)
 
+    @tool
+    def init_agent_template(
+        name: str,
+        description: str = "A new A2A agent",
+    ) -> str:
+        """Initialize ``agents/<name>/`` from the installed a2a-pack template.
+
+        Use this FIRST for a new project. It writes the same baseline files
+        as ``a2a init`` for the SDK version installed in this runtime:
+        ``agent.py``, ``a2a.yaml``, and ``requirements.txt``. After this,
+        edit those files with ``read_agent_file`` + ``write_agent_file`` to
+        implement the user's requested behavior.
+        """
+        try:
+            files = _render_a2a_init_template(name, description=description)
+            prefix = _agent_prefix(name)
+        except (OSError, ValueError) as exc:
+            return json.dumps({"error": str(exc)})
+        written: list[dict[str, Any]] = []
+        for path, content in files.items():
+            key = prefix + path
+            s3.put_object(
+                Bucket=bucket,
+                Key=key,
+                Body=content.encode("utf-8"),
+                ContentType="text/plain; charset=utf-8",
+            )
+            written.append({"path": key, "size": len(content)})
+        return json.dumps({"ok": True, "agent": name, "files": written})
+
     @tool
     def list_agent_files(name: str) -> str:
         """List every file under ``agents/<name>/`` in the user's workspace.
@@ -434,7 +465,7 @@ def build_tools(ctx: ToolContext) -> list[Any]:
         })
 
     return [
-        list_agent_files, write_agent_file, read_agent_file,
+        init_agent_template, list_agent_files, write_agent_file, read_agent_file,
         test_agent_in_sandbox, cp_deploy_tarball, cp_refresh_agent,
         list_a2a_pack, read_a2a_pack,
     ]
@@ -479,3 +510,37 @@ def _read_entrypoint(bundle: bytes) -> str | None:
 
 def _class_name(slug: str) -> str:
     return "".join(p.capitalize() for p in re.split(r"[-_]+", slug) if p) or "MyAgent"
+
+
+def _render_a2a_init_template(
+    name: str,
+    *,
+    description: str = "A new A2A agent",
+) -> dict[str, str]:
+    _validate_name(name)
+    class_name = _class_name(name)
+    return {
+        "agent.py": _render_sdk_template(
+            "agent.py.tmpl",
+            name=name,
+            class_name=class_name,
+            description=description,
+        ),
+        "a2a.yaml": _render_sdk_template(
+            "a2a.yaml.tmpl",
+            name=name,
+            class_name=class_name,
+        ),
+        "requirements.txt": _render_sdk_template("requirements.txt.tmpl"),
+    }
+
+
+def _render_sdk_template(template: str, /, **vars: str) -> str:
+    text = (
+        resources.files("a2a_pack.cli.templates")
+        .joinpath(template)
+        .read_text(encoding="utf-8")
+    )
+    for key, value in vars.items():
+        text = text.replace("{{ " + key + " }}", value)
+    return text