ComplexFuncBench
Models make function calls for 1,000 travel booking style samples that need several steps, user constraints, implicit parameter reasoning, long parameter values or 128K context.
The ComplexEval framework scores both the calls and the final answer.
- Made by
- Zhipu AI and Tsinghua University (THUDM)
- Released
- January 2025
- Kind
- Function calling
- Level
- University
- Scored
- Checked automatically
- Answers
- Agent task
- Tasks
- All public
- Strongest model tested
- GPT-4.1 mini #144 on the capability index
- Last in a launch post
- June 2025, dropped before it saturated
- Last model added
- June 2025
- Scores refreshed
- November 12th, 2026
In the authors’ words
Enhancing large language models (LLMs) with real-time APIs can help generate more accurate and up-to-date responses. However, evaluating the function calling abilities of LLMs in real-world scenarios remains under-explored due to the complexity of data collection and evaluation. In this work, we introduce ComplexFuncBench, a benchmark for complex function calling across five real-world scenarios. Compared to existing benchmarks, ComplexFuncBench encompasses multi-step and constrained function calling, which requires long-parameter filing, parameter value reasoning, and 128k long context. Additionally, we propose an automatic framework, ComplexEval, for quantitatively evaluating complex function calling tasks. Through comprehensive experiments, we demonstrate the deficiencies of state-of-the-art LLMs in function calling and suggest future directions for optimizing these capabilities. The data and code are available at https://github.com/THUDM/ComplexFuncBench.
Claude 3.5 Sonnet (October 2024) leads with 61% among models released by November 2024
Best score per entry from the benchmark's own leaderboard, read on November 12th, 2026. Where a model ran with several settings or harnesses, we keep its best. Names in gray aren't in our model list: fine-tunes, agent systems, products and older models. They don't count toward leaders.
Hunyuan-A13B-Instruct leads with 61.2%, claims included
Best score per model from every source, including labs’ own numbers and claims Epoch AI collected from reports and papers. Labs pick their own settings, so a claim can beat an independent run of the same model.
The newest model with a score here came out in November 2024, and nobody has tested a newer one. Among the 20 highest-ranked models on the capability index, these have no score yet:
- Claude Fable 5.2
-
Gemini 4 Carbon
- GPT-6 Astra
- Claude Opus 5.5
- and 16 more
- 1 Claude 3.5 Sonnet (October 2024) 61%
- 2 GPT-4o Aug 2024 60.5%
- 3 GLM-4-Long 57.1%
- 4 GPT-4 Turbo Apr 2024 49.5%
- 5 Claude 3.5 Haiku 45.8%
- 6
Qwen2.5-72B 40.1%
- 7
Mistral Large 2 Nov 2024 20.1%
- 8 GLM-4-9B 9.40%
- 9
Qwen2.5-7B 5.00%
- 10
Llama 3.1-405B 4.00%
- 11
Llama 3.1-70B 2.70%
- 12
Llama 3.1-8B 0.10%
Source: Official ComplexFuncBench leaderboard
- 1
Hunyuan-A13B-Instruct 61.2%
- 2 Claude 3.5 Sonnet (October 2024) 61%
- 3 GPT-4o Aug 2024 60.5%
- 4 GPT-4 Turbo Apr 2024 49.5%
- 5 GPT-4.1 mini 49.3%
- 6 Claude 3.5 Haiku 45.8%
- 7
Qwen2.5-72B 40.1%
- 8
Mistral Large 2 Nov 2024 20.1%
- 9 GLM-4-9B 9.40%
- 10 GPT-4.1 nano 5.70%
- 11
Qwen2.5-7B 5.00%
- 12
Llama 3.1-405B 4.00%
- 13
Llama 3.1-70B 2.70%
- 14
Llama 3.1-8B 0.10%
Sources: Labs’ model cards and official ComplexFuncBench leaderboard
| # | Entry | Score | Setting | Date | Source |
|---|---|---|---|---|---|
| 1 | Claude 3.5 Sonnet (October 2024) | 61% | Oct 2024 | Official leaderboard | |
| 2 | GPT-4o Aug 2024 | 60.5% | Aug 2024 | Official leaderboard | |
| 3 | GLM-4-Long | 57.1% | Official leaderboard | ||
| 4 | GPT-4 Turbo Apr 2024 | 49.5% | Apr 2024 | Official leaderboard | |
| 5 | Claude 3.5 Haiku | 45.8% | Oct 2024 | Official leaderboard | |
| 6 | | 40.1% | Sep 2024 | Official leaderboard | |
| 7 | | 20.1% | Nov 2024 | Official leaderboard | |
| 8 | GLM-4-9B | 9.40% | Jun 2024 | Official leaderboard | |
| 9 | | 5.00% | Sep 2024 | Official leaderboard | |
| 10 | | 4.00% | Jul 2024 | Official leaderboard | |
| 11 | | 2.70% | Jul 2024 | Official leaderboard | |
| 12 | | 0.10% | Jul 2024 | Official leaderboard |
| # | Model | Score | Setting | Date | Source |
|---|---|---|---|---|---|
| 1 | | 61.2% | Jun 2025 | Lab model card | |
| 2 | Claude 3.5 Sonnet (October 2024) | 61% | Oct 2024 | Official leaderboard | |
| 3 | GPT-4o Aug 2024 | 60.5% | Aug 2024 | Official leaderboard | |
| 4 | GPT-4 Turbo Apr 2024 | 49.5% | Apr 2024 | Official leaderboard | |
| 5 | GPT-4.1 mini | 49.3% | Apr 2025 | Lab model card | |
| 6 | Claude 3.5 Haiku | 45.8% | Oct 2024 | Official leaderboard | |
| 7 | | 40.1% | Sep 2024 | Official leaderboard | |
| 8 | | 20.1% | Nov 2024 | Official leaderboard | |
| 9 | GLM-4-9B | 9.40% | Jun 2024 | Official leaderboard | |
| 10 | GPT-4.1 nano | 5.70% | Apr 2025 | Lab model card | |
| 11 | | 5.00% | Sep 2024 | Official leaderboard | |
| 12 | | 4.00% | Jul 2024 | Official leaderboard | |
| 13 | | 2.70% | Jul 2024 | Official leaderboard | |
| 14 | | 0.10% | Jul 2024 | Official leaderboard |
Labs report scores for 3 models in their cards. Switch the scores above to rank them together.
Number one over time 2 models have held number one with claims included since its release in January 2025
Lab claims count from the day the card came out, independent runs from the model’s release. We draw one row each for the benchmark’s own leaderboard and what labs claim in their cards.
Sources: Official ComplexFuncBench leaderboard and labs’ model cards
Scores over time
All the scores we have, one dot each, so a model tested at several settings appears more than once.
Sources: Official ComplexFuncBench leaderboard and labs’ model cards
No launch post has listed it since June 2025
Launch posts from every lab that has listed it, one tick per post. Tall colored ticks include it, and short gray ones leave it out.
| Date | Launch post | Score | As the post writes it |
|---|---|---|---|
| Jun 27, 2025 | 61.2 | ComplexFuncBench | |
| Apr 14, 2025 | GPT-4.1 nano | 5.7 | ComplexFuncBench |
| Apr 14, 2025 | GPT-4.1 mini | 49.3 | ComplexFuncBench |
One system card reports it
Besides launch posts, we read the system cards, model cards and technical reports labs publish with a release. They report far more, including safety and frontier-risk tests.
| Date | Document | Score | As the document writes it | Section |
|---|---|---|---|---|
| Jun 26, 2025 | | 61.2 | ComplexFuncBench, slow-thinking (Table 3). Fast-thinking 74.0 (Table 4) | Capabilities |
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