~ LOSSY

pydantic-ai 2.61.0

truncation.tool-call-args · openai-responses

Back to results · Scenario

Requirements

IdLevelStatusEvidence
no-complete-partial-callMUSTSATISFIEDoutcome=raised; error signalled
cause-is-truncationMUSTNOT_OBSERVABLEfinish.value="length" (raw: ModelResponse.finish_reason); truth.finish="length"; error.category="validation"; structured.returned_as_success=false

What the provider sent

Finish
length
Raw finish
max_output_tokens
Text
null
Tool calls
[
  {
    "arguments": null,
    "arguments_parsed_ok": false,
    "arguments_raw": "{\"title\":\"Weekend Pottery Workshop\",\"",
    "id": "call_lLsu7YMQmuJzYwIjUOdF8uic",
    "name": "create_event"
  }
]
Usage
{
  "alternatives": {},
  "cached_input": 0,
  "input": 100,
  "output": 20,
  "raw": {
    "input_tokens": 100,
    "input_tokens_details": {
      "cache_write_tokens": 0,
      "cached_tokens": 0
    },
    "output_tokens": 20,
    "output_tokens_details": {
      "reasoning_tokens": 0
    },
    "total_tokens": 120
  },
  "reasoning": 0,
  "total": 120
}
Stream completed
null
Error
null
Wire excerpt
status: 200
content-type: application/json
body (json):
{
  "id": "resp_04ed45eb9c649570006acbfc064e7087d1bc256e42548bb4ae",
  "object": "response",
  "created_at": 1791753222,
  "status": "incomplete",
  "access_programs": null,
  "background": false,
  "billing": {
    "payer": "developer"
  },
  "completed_at": null,
  "error": null,
  "frequency_penalty": 0.0,
  "incomplete_details": {
    "reason": "max_output_tokens"
  },
  "instructions": null,
  "max_output_tokens": 20,
  "max_tool_calls": null,
  "model": "gpt-6-luna",
  "moderation": null,
  "output": [
    {
      "id": "fc_04ed45eb9c649570006acbfc06e08087d1a25f7b11c8d83e05",
      "type": "function_call",
      "status": "incomplete",
      "arguments": "{\"title\":\"Weekend Pottery Workshop\",\"",
      "call_id": "call_lLsu7YMQmuJzYwIjUOdF8uic",
      "name": "create_event"
    }
  ],
  "parallel_tool_calls": true,
  "presence_penalty": 0.0,
  "previous_response_id": null,
  "prompt_cache_key": null,
  "prompt_cache_retention": "24h",
  "reasoning": {
    "context": "all_turns",
    "effort": "none",
    "mode": "standard",
    "summary": null
  },
  "safety_identifier": null,
  "service_tier": "default",
  "store": true,
  "temperature": 1.0,
  "text": {
    "format": {
      "type": "text"
    },
    "verbosity": "medium"
  },
  "tool_choice": "required",
  "tool_usage": {
    "image_gen": {
      "input_tokens": 0,
      "input_tokens_details": {
        "image_tokens": 0,
        "text_tokens": 0
      },
      "output_tokens": 0,
      "output_tokens_details": {
        "image_tokens": 0,
        "text_tokens": 0
      },
      "total_tokens": 0
    },
    "web_search": {
      "num_requests": 0
    }
  },
  "tools": [
    {
      "type": "function",
      "description": "Create a calendar event.",
      "name": "create_event",
      "output_schema": null,
      "parameters": {
        "type": "object",
        "properties": {
          "title": {
            "type": "string"
          },
          "date": {
            "type": "string",
            "description": "YYYY-MM-DD"
          },
          "city": {
            "type": "string"
          },
          "attendees": {
            "type": "array",
            "items": {
              "type": "string"
            }
          }
        },
        "required": [
          "title",
          "date",
          "city",
          "attendees"
        ],
        "additionalProperties": false
      },
      "strict": true
    }
  ],
  "top_logprobs": 0,
  "top_p": 0.98,
  "truncation": "disabled",
  "usage": {
    "input_tokens": 100,
    "input_tokens_details": {
      "cache_write_tokens": 0,
      "cached_tokens": 0
    },
    "output_tokens": 20,
    "output_tokens_details": {
      "reasoning_tokens": 0
    },
    "total_tokens": 120
  },
  "user": null,
  "metadata": {}
}

What the library reported

Outcome
raised
Finish
{
  "raw": "max_output_tokens",
  "source": "ModelResponse.finish_reason",
  "surface": "raw",
  "value": "length"
}
Text
Value
null
Surface
absent
Tool calls
[
  {
    "arguments": {
      "INVALID_JSON": "{\"title\":\"Weekend Pottery Workshop\",\""
    },
    "arguments_parsed_ok": true,
    "arguments_raw": "{\"INVALID_JSON\":\"{\\\"title\\\":\\\"Weekend Pottery Workshop\\\",\\\"\"}",
    "id": "call_lLsu7YMQmuJzYwIjUOdF8uic",
    "name": "create_event"
  }
]
Usage
{
  "cached_input": 0,
  "input": 100,
  "output": 20,
  "reasoning": 0,
  "surface": {
    "cached_input": "raw",
    "input": "raw",
    "output": "raw",
    "reasoning": "raw",
    "total": "raw"
  },
  "total": 120
}
Stream
{
  "chunks_seen": null,
  "completed": null,
  "used": false
}
Error
Type
pydantic_ai.exceptions.UnexpectedModelBehavior
Message
Tool 'create_event' exceeded max retries count of 0. Consider raising the retry limit, or see the docs on tool retries: https://pydantic.dev/docs/ai/tools-toolsets/tools-advanced/#tool-retries
Category
validation
Retry after
null
Stack top
pydantic_ai/tool_manager.py:523
Unsupported reason
null
Full observation JSON
{
  "elapsed_ms": 419.3662852048874,
  "error": {
    "category": "validation",
    "message": "Tool 'create_event' exceeded max retries count of 0. Consider raising the retry limit, or see the docs on tool retries: https://pydantic.dev/docs/ai/tools-toolsets/tools-advanced/#tool-retries",
    "retry_after": null,
    "stack_top": "pydantic_ai/tool_manager.py:523",
    "type": "pydantic_ai.exceptions.UnexpectedModelBehavior"
  },
  "finish": {
    "raw": "max_output_tokens",
    "source": "ModelResponse.finish_reason",
    "surface": "raw",
    "value": "length"
  },
  "format": "wiretruth.observation/v1",
  "library": {
    "api": "Agent.run",
    "language": "python",
    "name": "pydantic-ai",
    "version": "2.61.0"
  },
  "notes": [],
  "outcome": "raised",
  "stream": {
    "chunks_seen": null,
    "completed": null,
    "used": false
  },
  "structured": {
    "attempted": false,
    "returned_as_success": false,
    "value": null
  },
  "text": {
    "surface": "absent",
    "value": null
  },
  "tool_calls": [
    {
      "arguments": {
        "INVALID_JSON": "{\"title\":\"Weekend Pottery Workshop\",\""
      },
      "arguments_parsed_ok": true,
      "arguments_raw": "{\"INVALID_JSON\":\"{\\\"title\\\":\\\"Weekend Pottery Workshop\\\",\\\"\"}",
      "id": "call_lLsu7YMQmuJzYwIjUOdF8uic",
      "name": "create_event"
    }
  ],
  "unsupported_reason": null,
  "usage": {
    "cached_input": 0,
    "input": 100,
    "output": 20,
    "reasoning": 0,
    "surface": {
      "cached_input": "raw",
      "input": "raw",
      "output": "raw",
      "reasoning": "raw",
      "total": "raw"
    },
    "total": 120
  }
}

Fixture

recorded openai-responses/truncation.tool-call-args

ProvenanceValue
Recorded at2026-10-11T21:13:42Z
Requested modelgpt-6-luna
Returned modelgpt-6-luna
CI runhttps://github.com/kartsan03/wiretruth/actions/runs/38175457862

Reproduce

wiretruth serve openai-responses/truncation.tool-call-args

Plain-library snippet from the shim manifest.

OpenAIResponsesModel(model, provider=OpenAIProvider(base_url=WIRETRUTH_BASE_URL_OPENAI_RESPONSES, api_key=WIRETRUTH_API_KEY))

Upstream

reported Issue

Fixed in: not specified

Reported in a comment on the token-limit issue: https://github.com/pydantic/pydantic-ai/issues/12399#issuecomment-6780480981. Tool-call arguments cut off at the limit fail validation and end in the per-tool retry limit (UnexpectedModelBehavior: Tool 'create_event' exceeded max retries count of 0), not in IncompleteToolCall; reproduced on 2.61.0 and 2.66.0 with an ExternalToolset.

History

VersionGrade
2.61.0~ LOSSY
2.56.0~ LOSSY