update agent guide

docs/design_pattern/agent.md

@@ -54,7 +54,7 @@ The core of building **high-performance** and **reliable** agents boils down to:
 
 1. **Context Management:** Provide *relevant, minimal context.* For example, rather than including an entire chat history, retrieve the most relevant via [RAG](./rag.md). Even with larger context windows, LLMs still fall victim to ["lost in the middle"](https://arxiv.org/abs/2307.03172), overlooking mid-prompt content.
 
-2. **Action Space:** Provide *a well-structured and unambiguous* set of actions—avoiding overlap like separate `read_databases` or  `read_csvs`. Instead, import CSVs into the database and then use one parameterized (e.g., table name) or programmable action (e.g., via SQL) to query data.
+2. **Action Space:** Provide *a well-structured and unambiguous* set of actions—avoiding overlap like separate `read_databases` or  `read_csvs`. Instead, import CSVs into the database.
 
 ## Example Good Action Design
 
@@ -62,6 +62,10 @@ The core of building **high-performance** and **reliable** agents boils down to:
 
 **Overview-zoom-in:** First provide high-level structure (table of contents, summary), then allow drilling into details (raw texts).
 
+**Parameterized/Programmable:** Instead of fixed actions, enable parameterized (columns to select) or programmable (SQL queries) actions, for example, to read CSV files.
+
+**Backtracking:** Let the agent undo the last step instead of restarting entirely, preserving progress when encountering errors or dead ends.
+
 ## Example: Search Agent
 
 This agent: