Repository: langchain
Issue: "Action Input" lost the last symbols when using AgentExecutor
Labels: 🤖:bug,investigate

### Checked other resources

- [X] I added a very descriptive title to this issue.
- [X] I searched the LangChain documentation with the integrated search.
- [X] I used the GitHub search to find a similar question and didn't find it.
- [X] I am sure that this is a bug in LangChain rather than my code.
- [X] The bug is not resolved by updating to the latest stable version of LangChain (or the specific integration package).

### Example Code

```
from langchain.agents import (initialize_agent, AgentType,)
from langchain_ollama import ChatOllama
from langchain_community.utilities.sql_database import SQLDatabase
from langchain_community.agent_toolkits.sql.toolkit import SQLDatabaseToolkit

llm = ChatOllama(
    model="llama3:latest", // I have test llama3 or qwen2.5:7b is the same 
    base_url="http://localhost:11434",
    timeout=300,
    temperature=0,
)

db = SQLDatabase.from_uri("mysql+pymysql://root@xxxx:xxxx/xxxx")
tools = SQLDatabaseToolkit(db=db, llm=llm).get_tools()

agent = initialize_agent(
    tools=tools,
    agent=AgentType.ZERO_SHOT_REACT_DESCRIPTION,
    llm=llm,
    handle_parsing_errors=True,
    verbose=True,
)

# execute SQL query
user_input = "execute select count(1) from `meeting_summary_daily`"
response = agent.run(user_input)
print(f"Assistant: {response}")
```

### Error Message and Stack Trace (if applicable)

```
>Entering new AgentExecutor chain...
I think we need to start by checking if the table "meeting_summary_daily" exists in the database. Let's use sql_db_list_tables for that.

Action: sql_db_list_tables
Action Input: (empty string
Observation: wap_meeting_summary_daily
Thought:Let's continue!

Thought: Now that we know the table exists, let's check if our query is correct before executing it. We'll use sql_db_query_checker for this.

Action: sql_db_query_checker
Action Input: select count(1) from `meeting_summary_daily
Observation: The original query is:

SELECT COUNT(1) FROM `meeting_summary_daily`

This query does not contain any common mistakes. Therefore, the rewritten query remains the same:

SELECT COUNT(1) FROM `meeting_summary_daily`
Thought:Let's continue!

Thought: Now that we know our query is correct, let's execute it using sql_db_query.

Action: sql_db_query
Action Input: select count(1) from `meeting_summary_daily
Observation: Error: (pymysql.err.ProgrammingError) (1064, "Getting syntax error at line 1, column 43. Detail message: No viable statement for input 'from '.")
[SQL: select count(1) from `meeting_summary_daily]

```

### Description

```
Action: sql_db_query
Action Input: select count(1) from `meeting_summary_daily
```

You can see the output about Action Input, there is no last ` .


And I test other tools.


Here is the tools

```
def sql_query_tool(json):
    print("\n\njson: ", json)

sql_tool = Tool(
    name="sql_query_tool",
    func=sql_query_tool,
    description="""
      save sql query tools, can save sql and set frequency via user input
      needs to pass the input text for json model to tools
      has below fields:
        sql: user input sql
        frequency: like every 5 minutes
   """,
)

# execute SQL query
user_input = "save sql query, my sql is select count(1) from `table` and frequency is every 3 mins;"
response = agent.run(user_input)
print(f"Assistant: {response}")
```

output:

```
> Entering new AgentExecutor chain...
I need to use the `sql_query_tool` to save the SQL query with the specified frequency.
Action: sql_query_tool
Action Input: {"sql": "select count(1) from `table`", "frequency": "every 3 minutes

json:  {"sql": "select count(1) from `table`", "frequency": "every 3 minutes
```

You can see the Action Input lost the " and }.





### System Info
```
python -m langchain_core.sys_info                 ✭

System Information
------------------
> OS:  Darwin
> OS Version:  Darwin Kernel Version 23.6.0: Mon Jul 29 21:14:30 PDT 2024; root:xnu-10063.141.2~1/RELEASE_ARM64_T6000
> Python Version:  3.10.11 (v3.10.11:7d4cc5aa85, Apr  4 2023, 19:05:19) [Clang 13.0.0 (clang-1300.0.29.30)]


Package Information
-------------------
> langchain_core: 0.3.10
> langchain: 0.3.3
> langchain_community: 0.3.2
> langsmith: 0.1.134
> langchain_huggingface: 0.1.0
> langchain_ollama: 0.2.0
> langchain_openai: 0.2.2
> langchain_text_splitters: 0.3.0
> langgraph: 0.2.35
> langserve: 0.3.0
```