BerriAI/litellm · error · OCIError

Tool call `id` must be a string

Error message

Tool call `id` must be a string

What it means

Each tool call in an assistant message must carry a string 'id' so LiteLLM can map it into OCIToolCall(id=...). A missing, None, or non-string id raises OCIError(400) 'Tool call `id` must be a string' client-side. The id is what later role='tool' messages reference via tool_call_id, so it cannot be omitted.

Source

Thrown at litellm/llms/oci/chat/generic.py:125

        role=open_ai_to_generic_oci_role_map[role],
        content=new_content,
        toolCalls=None,
        toolCallId=None,
    )


def adapt_messages_to_generic_oci_standard_tool_call(role: str, tool_calls: list) -> OCIMessage:
    """Convert an assistant tool-call message to OCI format."""
    tool_calls_formatted: Final = []
    for tool_call in tool_calls:
        if not isinstance(tool_call, dict):
            raise OCIError(status_code=400, message="Each tool call must be a dictionary")
        if tool_call.get("type") != "function":
            raise OCIError(status_code=400, message="OCI only supports function tool calls")

        tool_call_id = tool_call.get("id")
        if not isinstance(tool_call_id, str):
            raise OCIError(status_code=400, message="Tool call `id` must be a string")

        tool_function = tool_call.get("function")
        if not isinstance(tool_function, dict):
            raise OCIError(status_code=400, message="Tool call `function` must be a dictionary")

        function_name = tool_function.get("name")
        if not isinstance(function_name, str):
            raise OCIError(status_code=400, message="Tool call `function.name` must be a string")

        arguments = tool_call["function"].get("arguments", "{}")
        if not isinstance(arguments, str):
            raise OCIError(
                status_code=400,
                message="Tool call `function.arguments` must be a JSON string",
            )

        tool_calls_formatted.append(
            OCIToolCall(

View on GitHub (pinned to 6c2dcb801b)

Solutions

1. Give every tool call a unique string id and reuse it in the matching tool result's tool_call_id (e.g. 'call_001').
2. If generating synthetic history, mint ids with uuid4().hex or a counter.
3. Pre-flight check: all(isinstance(tc.get('id'), str) and tc['id'] for tc in msg['tool_calls']).

Example fix

# before
{'type':'function','function':{'name':'f','arguments':'{}'}}

# after
{'id':'call_001','type':'function','function':{'name':'f','arguments':'{}'}}
# and the tool reply: {'role':'tool','tool_call_id':'call_001','content':'42'}

import uuid

for tc in msg.get('tool_calls') or []:
    if not isinstance(tc.get('id'), str) or not tc['id']:
        tc['id'] = f'call_{uuid.uuid4().hex[:8]}'

def tool_call_has_string_id(tc: object) -> bool:
    return isinstance(tc, dict) and isinstance(tc.get('id'), str) and bool(tc['id'])

When it happens

Trigger: Hand-constructing assistant tool call history without an 'id' (e.g. {'type':'function','function':{...}}), or with id set to an integer/None, in a request to an oci/ GENERIC model.

Common situations: Fabricating synthetic assistant turns for few-shot tool use and forgetting the id; a database schema storing tool calls without ids; trimming ids 'to save tokens' in long conversations.

Related errors

• Tool call `function.name` must be a string
• Tool result message must have a string `tool_call_id`
• Each tool call must be a dictionary
• OCI only supports function tool calls
• Tool call `function` must be a dictionary

AI-assisted analysis of BerriAI/litellm@6c2dcb801b (2026-08-15). Data as JSON: /api/errors/55dad91d9fb2663b. Report an issue: GitHub.