Benchmark Almanac

ComplexFuncBench

Claude 3.5 Sonnet (October 2024) 61% leads since January 2025
Hunyuan-A13B-Instruct 61.2% leads since June 2025
Dropped

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.

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.

Abstract of ComplexFuncBench: Exploring Multi-Step and Constrained Function Calling under Long-Context Scenario (arXiv:2501.10132, CC0)
12
Entries on its own leaderboard, 11 models we track
3
Launch posts list it, from 2 labs
1
System card reports it, from 1 lab

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:

  1. 1 Claude 3.5 Sonnet (October 2024) 61%
  2. 2 GPT-4o Aug 2024 60.5%
  3. 3 GLM-4-Long 57.1%
  4. 4 GPT-4 Turbo Apr 2024 49.5%
  5. 5 Claude 3.5 Haiku 45.8%
  6. 6 Qwen2.5-72B 40.1%
  7. 7 Mistral Large 2 Nov 2024 20.1%
  8. 8 GLM-4-9B 9.40%
  9. 9 Qwen2.5-7B 5.00%
  10. 10 Llama 3.1-405B 4.00%
  11. 11 Llama 3.1-70B 2.70%
  12. 12 Llama 3.1-8B 0.10%

Source: Official ComplexFuncBench leaderboard

#EntryScoreSettingDateSource
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 Qwen2.5-72B 40.1% Sep 2024 Official leaderboard
7 Mistral Large 2 Nov 2024 20.1% Nov 2024 Official leaderboard
8 GLM-4-9B 9.40% Jun 2024 Official leaderboard
9 Qwen2.5-7B 5.00% Sep 2024 Official leaderboard
10 Llama 3.1-405B 4.00% Jul 2024 Official leaderboard
11 Llama 3.1-70B 2.70% Jul 2024 Official leaderboard
12 Llama 3.1-8B 0.10% Jul 2024 Official leaderboard
#ModelScoreSettingDateSource
1 Hunyuan-A13B-Instruct 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 Qwen2.5-72B 40.1% Sep 2024 Official leaderboard
8 Mistral Large 2 Nov 2024 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 Qwen2.5-7B 5.00% Sep 2024 Official leaderboard
12 Llama 3.1-405B 4.00% Jul 2024 Official leaderboard
13 Llama 3.1-70B 2.70% Jul 2024 Official leaderboard
14 Llama 3.1-8B 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.

Anthropic OpenAI Tencent
Own leaderboard Not tested since Jan 2025
Lab claims Not tested since Jun 2025

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.

On the benchmark’s own leaderboard Reported by the lab in its model card Best so far
0% 20% 40% 60% 80% 100% 2024 2025 Near the ceiling (85%) Hunyuan-A13B-Instruct Claude 3.5 Sonnet (October 2024) GPT-4 Turbo 0% 20% 40% 60% 80% 100% 2024 2025 Near the ceiling (85%) Hunyuan-A13B-Instruct GPT-4o

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.

OpenAI
Tencent
DateLaunch postScoreAs the post writes it
Jun 27, 2025 Hunyuan-A13B-Instruct 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.

DateDocumentScoreAs the document writes itSection
Jun 26, 2025 Hunyuan-A13B-Instruct technical report 61.2 ComplexFuncBench, slow-thinking (Table 3). Fast-thinking 74.0 (Table 4) Capabilities

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