CompToolBench: Measuring Compositional Tool-Use Generalization in LLMs

Dataset Summary

CompToolBench is a benchmark for evaluating how well large language models generalize from simple, single-tool calls to complex, multi-step compositional tool use. It contains 200 tasks spanning four composition levels of increasing structural complexity, built on top of 106 deterministic tool simulators covering 9 functional categories.

The key insight behind CompToolBench is the composition gap: models that can reliably call individual tools often fail dramatically when those same tools must be composed into chains, parallel fan-outs, or directed acyclic graphs (DAGs). CompToolBench quantifies this gap with fine-grained diagnostic metrics.

Key Features

• 4 composition levels: single calls (L0), sequential chains (L1), parallel fan-outs (L2), and full DAGs with branching + merging (L3)
• 106 deterministic tool simulators: no external API dependencies, fully reproducible
• Fine-grained scoring: tool selection accuracy, argument accuracy, data-flow correctness, completion rate
• 18-model leaderboard: spanning cloud APIs (Mistral, Cohere, Groq, Cerebras, OpenRouter) and local models (Ollama)
• Composition gap metric: directly measures how much accuracy degrades as structural complexity increases

Dataset Structure

Each example in the dataset contains the following fields:

Field	Type	Description
task_id	string	Unique identifier (e.g., L0_node_0001, L3_dag_0153)
level	string	Composition level: L0_node, L1_chain, L2_parallel, or L3_dag
prompt	string	Natural language instruction given to the model
available_tools	list[string]	Tool names provided to the model (includes distractors)
expected_trace	object	Ground-truth execution plan with steps, dependencies, and arguments
expected_final_answer	string	JSON-serialized expected output
num_steps	int	Number of tool calls in the expected trace
num_tools_offered	int	Number of tools offered (correct + distractors)
category	string	Functional category of the task
pattern	string	Composition pattern (e.g., retrieve-transform, fan-out-compare)

Expected Trace Structure

Each step in expected_trace.steps contains:

• step_id: Step identifier (e.g., step_1)
• tool_name: Which tool to call
• arguments: JSON-serialized expected arguments
• depends_on: List of step IDs this step depends on (defines the DAG structure)
• output_key: Variable name for the step's output (used by downstream steps)

Composition Levels

Level	Name	Description	Tasks	Avg Steps	Avg Tools Offered
L0	Single Node	One tool call, no composition	48	1.0	4.0
L1	Chain	Sequential pipeline (A -> B)	64	2.0	5.0
L2	Parallel	Independent fan-out (A || B || C)	40	2.8	4.2
L3	DAG	Full directed acyclic graph with branching and merging	48	4.4	6.6

Task Categories

Tasks cover 9 functional categories: chain, communication, computation, dag, external_services, information_retrieval, parallel, text_processing, and time_scheduling.

Composition Patterns

Over 40 distinct composition patterns are represented, including retrieve-transform, fan-out-compare, chain-fanout-merge-chain, parallel-merge-chain, true-dag-parallel-reads-merge, and many more. See the paper for full details.

Leaderboard

Results from evaluating 18 models (10 cloud, 8 local) on all 200 tasks. Models are ranked by overall accuracy. All models achieve 100% tool selection accuracy (when they issue a call, they name the correct tool).

Cloud Models

Model	Provider	L0	L1	L2	L3	Overall	Delta
Llama 3.1 8B	Groq	27.1	75.8	87.1	76.0	66.4	-48.9
Command A	Cohere	45.8	62.7	87.8	40.8	58.4	5.1
Mistral Small	Mistral	45.8	59.7	87.6	40.9	57.5	4.9
Command R+	Cohere	43.8	57.5	88.0	40.3	56.2	3.4
Llama 3.1 8B	Cerebras	31.2	66.1	81.2	46.4	56.0	-15.1
Mistral Large	Mistral	39.6	59.5	87.9	38.5	55.4	1.1
Mistral Medium	Mistral	43.8	57.5	87.9	36.3	55.2	7.4
Gemini 2.0 Flash	OpenRouter	39.6	52.4	85.7	39.0	52.8	0.6
GPT-OSS 120B	Cerebras	45.8	56.3	56.1	29.0	47.2	16.8
Llama 4 Scout 17B	Groq	37.5	49.6	55.8	7.0	37.7	30.5

Local Models (Ollama)

Model	Provider	L0	L1	L2	L3	Overall	Delta
Granite4 3B	Ollama	45.8	57.3	56.1	30.2	47.8	15.6
Granite4 1B	Ollama	41.7	56.3	55.9	29.9	46.4	11.8
Mistral 7B	Ollama	43.8	57.7	49.2	30.5	46.1	13.3
Llama 3.1 8B	Ollama	39.6	56.7	56.1	29.5	45.9	10.1
Mistral Nemo 12B	Ollama	37.5	58.4	51.0	31.8	45.5	5.7
Qwen 2.5 7B	Ollama	39.6	56.7	53.8	25.8	44.6	13.8
Mistral Small 24B	Ollama	37.5	51.1	47.7	22.6	40.3	14.9
Qwen3 8B	Ollama	35.4	52.0	36.9	21.8	37.7	13.7

Aggregate Statistics

Segment	L0	L1	L2	L3	Overall	Delta
All models avg.	40.0	58.0	67.3	34.2	49.8	5.8
Cloud avg.	40.0	59.7	80.5	39.4	54.3	0.6
Local avg.	40.1	55.8	50.8	27.8	44.3	12.3

Delta = L0 accuracy minus L3 accuracy (positive means degradation at higher composition levels). Models marked with a dagger in the paper exhibit a Selection Gap, where L0 accuracy is lower than the average of L1-L3.

Usage

Loading the Dataset

from datasets import load_dataset

dataset = load_dataset("mdarahmanxAI/comptoolbench", split="test")

# Browse tasks by composition level
l3_tasks = dataset.filter(lambda x: x["level"] == "L3_dag")
print(f"L3 DAG tasks: {len(l3_tasks)}")
print(l3_tasks[0]["prompt"])

Evaluating a Model

CompToolBench evaluates models by comparing their tool-call traces against the expected trace. The evaluation harness is available in the GitHub repository.

import json

for task in dataset:
    # 1. Build the tool-use prompt from task["prompt"] and task["available_tools"]
    # 2. Send to your model with the tool schemas
    # 3. Compare the model's tool calls against:
    trace = json.loads(task["expected_trace"])
    answer = json.loads(task["expected_final_answer"])

    # Scoring dimensions:
    #   - Tool selection: did the model call the right tools?
    #   - Argument accuracy: were the arguments correct?
    #   - Data flow: did outputs flow correctly between steps?
    #   - Completion: did all required steps execute?

Scoring Metrics

Metric	Description
Overall Accuracy	Weighted combination of all sub-metrics
Tool Selection	Whether the model called the correct tool names
Argument Accuracy	Whether arguments matched expected values
Data Flow Accuracy	Whether inter-step data dependencies were satisfied
Completion Rate	Fraction of expected steps that were executed
Composition Gap	L0 accuracy minus Lk accuracy (measures degradation)

Citation

If you use CompToolBench in your research, please cite:

@article{rahmaan2026comptoolbench,
  title={CompToolBench: Measuring Compositional Tool-Use Generalization in Large Language Models},
  author={Rahmaan, Rony},
  journal={arXiv preprint},
  year={2026}
}

License

This dataset is released under the Creative Commons Attribution 4.0 International (CC BY 4.0) license. You are free to share and adapt the dataset for any purpose, provided you give appropriate credit.

Links

• Paper: arXiv (coming soon)
• Code: GitHub
• Demo: HuggingFace Spaces