MiniCPM5-1B-Agentic-Tooluse-v3-Merged-FP16 — Small Function-Calling LLM for vLLM / SGLang / Transformers

MiniCPM5-1B-Agentic-Tooluse-v3 is a 1-billion-parameter open-weight function-calling model merged into a single full-precision FP16 checkpoint — no adapter loading, no PEFT setup, no extra dependencies. Load it directly with transformers, serve it with vLLM or SGLang, and start calling tools immediately.

If you are looking for a small function-calling LLM for production serving, a 1B tool-use model for vLLM or SGLang, a compact open-weight alternative to GPT-4o / Claude function calling, or a locally deployable structured-output model for agent pipelines, this is the single-file, deploy-anywhere version.

74.67% exact-argument accuracy on a held-out 300-example benchmark — trained with QLoRA supervised fine-tuning followed by GRPO reinforcement learning, rewarding exact function-name and argument-value correctness.

Why this model

MiniCPM5-1B-Agentic-Tooluse-v3 is fine-tuned specifically to parse a tool schema and a natural-language user request, then emit a structured, correctly-named, correctly-valued function call — the exact skill that powers LangChain agents, LlamaIndex pipelines, AutoGen, CrewAI, MCP tool servers, ReAct loops, and home-automation assistants.

Unlike most small open tool-calling models that stop at supervised fine-tuning, this model goes further with GRPO reinforcement learning on top of the SFT checkpoint, specifically rewarding the two hardest parts of tool calling: choosing the right function name and getting every argument value exactly right.

Compared to GPT-4o / Claude for function calling: this model is 100% free, runs locally, keeps all data private, has zero per-call cost, and is fine-tunable — it trades some absolute accuracy for massive gains in cost, latency, and privacy. The merged FP16 format means you can load it with a single AutoModelForCausalLM.from_pretrained() call, just like any base model.

Why this model

MiniCPM5-1B-Agentic-Tooluse-v3 is fine-tuned specifically for agentic tool/function calling: given a tool schema and a natural-language request, it reliably produces a correctly-named, correctly-structured, correctly-valued function call — the exact capability that powers LangChain/LlamaIndex/AutoGen/CrewAI agents, MCP tool servers, ReAct-style loops, and home-automation assistants.

This release combines QLoRA supervised fine-tuning with a GRPO reinforcement-learning refinement stage, specifically optimized to improve exact function-name selection and exact argument-value correctness — historically the two hardest failure modes for small (~1B) tool-calling models.

Results

Evaluated on a held-out 300-example test slice drawn from a seeded shuffle of ToolACE (see Split integrity). The base-model column is the same model with the same prompt and no adapter.

The published weights are SFT + GRPO (see GRPO / RLVR). The SFT column is kept because every negative result below is measured against it.

GRPO buys +0.0100 on args_exact, the metric that matters here, and gives back 0.0034 (one test example each) on expected_name and arg_key_overlap. That trade is reported rather than hidden: the mean moves only +0.0006, so this is a targeted gain on the hardest metric, not a broad improvement.

Full 8-metric benchmark (held-out test set, n=300)

This table mirrors the evaluation format from v2 and shows Base, v2, and v3 side-by-side across all 8 metrics using a single consistent harness and held-out test slice:

What the additional metrics mean:

• no_schema_copy_rate — the model did not copy the tool schema's own field description verbatim into an argument value.
• no_repetition_rate — the completion did not contain a duplicated function-call block or degenerate repeated-phrase loop. This model has a known weakness here: it often continues generating filler content after the tool call completes. Use a parser that extracts the first completed <function>...</function> block.
• stopped_cleanly_rate — the model naturally stopped immediately after the completed </function> tag with no trailing tokens. Use a parser that treats the first completed <function>...</function> block as the action boundary — do not rely on natural end-of-generation.

Model details

• Base model: openbmb/MiniCPM5-1B

• Architecture: Llama-style causal language model, ~1.08B parameters

• Format: merged full weights, safetensors, FP16 — no adapter/PEFT loading required

• Training pipeline: QLoRA SFT on tool-calling trajectories → GRPO reinforcement learning targeting exact argument correctness

• Compatible with: transformers, vLLM, SGLang, TGI, and any standard Hugging Face causal-LM serving pipeline

Quickstart

from transformers import AutoModelForCausalLM, AutoTokenizer

tok = AutoTokenizer.from_pretrained("ewinregirgojr/MiniCPM5-1B-Agentic-Tooluse-v3-Merged-FP16")

model = AutoModelForCausalLM.from_pretrained("ewinregirgojr/MiniCPM5-1B-Agentic-Tooluse-v3-Merged-FP16")

# Use tok.apply_chat_template(messages, tools=[...]) with your function/tool schema,

# then generate as usual — the model emits a structured function call.

vLLM:

vllm serve ewinregirgojr/MiniCPM5-1B-Agentic-Tooluse-v3-Merged-FP16

Ideal use cases

• Production agent backends that need a fast, cheap, self-hosted function-calling model

• LangChain / LlamaIndex / AutoGen / CrewAI / MCP-based agents needing a small, reliable tool-calling backbone

• On-device and edge deployments where a 7B+ model isn't an option

• High-throughput services where per-request cost and latency matter more than squeezing out the last few points of accuracy from a much larger model

• Teams that want a fully open-weight, fine-tunable starting point instead of depending on a closed API for structured tool calls

Base model architecture

MiniCPM5-1B uses a standard LlamaForCausalLM architecture:

Thinking mode

MiniCPM5-1B has a built-in <think>...</think> chat template. The same checkpoint can act as a fast assistant or a deliberate chain-of-thought reasoner — controlled by a single flag:

# Fast mode — recommended for tool calling (thinking OFF)
prompt = tokenizer.apply_chat_template(
    messages, tools=tools, add_generation_prompt=True,
    enable_thinking=False,
    tokenize=False,
)

# Reasoning mode (thinking ON — NOT recommended for tool calling)
prompt = tokenizer.apply_chat_template(
    messages, tools=tools, add_generation_prompt=True,
    enable_thinking=True,
    tokenize=False,
)

Important: always use enable_thinking=False for tool/function calling. With thinking ON the model spends its token budget inside <think>...</think> and may not reach a completed function call. All benchmark numbers in this card use thinking OFF.

Citation

If you use this model, please cite the base model paper:

@article{minicpm4,
  title   = {MiniCPM4: Ultra-Efficient LLMs on End Devices},
  author  = {MiniCPM Team},
  journal = {arXiv preprint arXiv:2506.07900},
  year    = {2025}
}

And the ToolACE dataset used for fine-tuning:

@article{toolace,
  title   = {ToolACE: Winning the Points of LLM Function Calling},
  author  = {Liu, Ying and others},
  journal = {arXiv preprint arXiv:2409.00920},
  year    = {2024}
}

ModelScope

The base model is also available on ModelScope (for users in China and East Asia):

• OpenBMB/MiniCPM5-1B on ModelScope

(The fine-tuned adapter/GGUF builds are currently HuggingFace-only.)

Related repos

v3 model family (this release)

Previous releases

FAQ

Do I need the adapter repo too? No — this repo already contains the fully merged weights. Use the adapter repo only if you want to load it on top of base MiniCPM5-1B yourself or continue fine-tuning.

What's the difference between this and the GGUF repo? This is full-precision FP16 safetensors for GPU-backed serving frameworks (transformers, vLLM, SGLang). The GGUF repo is quantized for CPU-friendly local inference via llama.cpp/Ollama/LM Studio.

How was v3 trained differently from v2? v3 continues from the v2-era recipe with an additional QLoRA SFT pass plus a GRPO reinforcement-learning stage explicitly rewarding exact argument-value correctness, which is what drives the args_exact improvement shown above.

Base model

Built on MiniCPM5-1B by OpenBMB.

Limitations