What causes "Parse code error for {arguments}" in FoundationAgents/MetaGPT?

Retry the completion (a fresh sample usually produces well-formed quoted arguments).

FoundationAgents/MetaGPT · error · ValueError

Parse code error for

Error message

Parse code error for {arguments}

What it means

OpenAIGPTAPI._parse_arguments extracts a code block from a tool-call's arguments using a quote/backtick regex; if no quoted code segment is found (re.findall returned nothing and code_value stays None), it raises ValueError('Parse code error for ...'). The language is defaulted to python, but the code itself is mandatory.

Solutions

Retry the completion (a fresh sample usually produces well-formed quoted arguments).
Increase max_token limits so the code block is not truncated mid-quote.
Switch to a stronger model for tool/function calling (arguments format adherence varies).
Catch the ValueError and apply a lenient fallback parser that treats the whole arguments string as code.

Example fix

# before
arguments = '{"language": "python"}'  # no quoted code -> ValueError

# after (ensure model emits quoted code, or fall back)
try:
    parsed = provider._parse_arguments(arguments)
except ValueError:
    parsed = {"language": "python", "code": arguments}

Defensive patterns

Strategy: try-catch

Validate before calling

import re

def looks_parseable(arguments: str) -> bool:
    return bool(re.search(r'(["' + "'`" + r']{3}|["' + "'` + r'])([\s\S]*?)\1', arguments))

Try / catch

try:
    parsed = provider.get_choice_function_arguments(rsp)
except ValueError as e:
    if "Parse code error" in str(e):
        args = rsp.choices[0].message.tool_calls[0].function.arguments
        parsed = {"language": "python", "code": args}  # lenient fallback
    else:
        raise

Prevention

Use function-calling-capable models for code actions
Raise max_token limits to avoid mid-quote truncation
Implement a lenient fallback parser for unquoted code arguments

When it happens

Trigger: get_choice_function_arguments on a response where tool_calls[0].function.arguments contains code without enclosing quotes/backticks, or arguments that are JSON like {"language": "javascript"} with the code field missing; the regex finds no quoted payload and the raise fires.

Common situations: Weaker models emitting malformed tool-call JSON, truncation at max tokens cutting off the code quotes, or actions whose arguments only carry metadata; typically seen in MetaGPT ActionNode/DataInterpreter tool flows.

Related errors

AI-assisted analysis of FoundationAgents/MetaGPT@11cdf466d0 (2026-08-14). Data as JSON: /api/errors/938346afed0cff8f. Report an issue: GitHub.

Appendix: source

Thrown at metagpt/provider/openai_api.py:225

        if "language" not in arguments and "code" not in arguments:
            logger.warning(f"Not found `code`, `language`, We assume it is pure code:\n {arguments}\n. ")
            return {"language": "python", "code": arguments}

        # 匹配language
        language_pattern = re.compile(r'[\"\']?language[\"\']?\s*:\s*["\']([^"\']+?)["\']', re.DOTALL)
        language_match = language_pattern.search(arguments)
        language_value = language_match.group(1) if language_match else "python"

        # 匹配code
        code_pattern = r'(["\'`]{3}|["\'`])([\s\S]*?)\1'
        try:
            code_value = re.findall(code_pattern, arguments)[-1][-1]
        except Exception as e:
            logger.error(f"{e}, when re.findall({code_pattern}, {arguments})")
            code_value = None

        if code_value is None:
            raise ValueError(f"Parse code error for {arguments}")
        # arguments只有code的情况
        return {"language": language_value, "code": code_value}

    # @handle_exception
    def get_choice_function_arguments(self, rsp: ChatCompletion) -> dict:
        """Required to provide the first function arguments of choice.

        :param dict rsp: same as in self.get_choice_function(rsp)
        :return dict: return the first function arguments of choice, for example,
            {'language': 'python', 'code': "print('Hello, World!')"}
        """
        message = rsp.choices[0].message
        if (
            message.tool_calls is not None
            and message.tool_calls[0].function is not None
            and message.tool_calls[0].function.arguments is not None
        ):
            # reponse is code

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