ActDecor

AI commentary layer for Python pipelines.

ActDecor provides a decorator wrapper that can be attached to any Python function. It executes your function normally, then sends the return value (and optional arguments) to an LLM and returns both the original value and a concise summary.

Under the hood ActDecor dispatches through the unified endpoint from ActLLMInfer — one completion() call across every supported provider, selected by a single provider/model string (LiteLLM-style).

It can also ask ActRouter which LLM is the best fit for the wrapped function, cache that choice in a function inventory file, and reuse it on subsequent calls.

Installation

pip install -e .

Quick start (unified endpoint)

from actdecor import summarize_with_llm

@summarize_with_llm(model="openai/gpt-4o-mini", completion_params={"temperature": 0})
def run_report(region: str) -> dict:
    return {
        "region": region,
        "revenue": 128_000,
        "cost": 92_500,
        "delta_vs_plan": -8.1,
    }

result = run_report("US-West")

print(result.value)       # original function output
print(result.commentary)  # LLM-generated summary
print(result.info)        # metadata (model, routing, etc.)

The model argument accepts any string actllminfer.completion accepts: "openai/gpt-4o-mini", "anthropic/claude-haiku-4-5", "deepseek/deepseek-chat", "kimi/moonshot-v1-8k", "zhipuai/glm-4-plus", "nvidia_nim/meta/llama-3.3-70b-instruct", etc. Per-call generation knobs (temperature, max_tokens, tools, response_format, stop …) go in completion_params; everything else (api_key, base_url, request_timeout …) is forwarded to the underlying client the first time it is constructed.

Legacy llm= (chain-style) path

If you prefer to construct a provider class yourself — or you need to stub the LLM out in tests — pass llm= instead of model=. ActDecor wires it into a prompt | llm | StrOutputParser chain just like before:

from actllminfer import ChatOpenAI
from actdecor import summarize_with_llm

llm = ChatOpenAI(model="gpt-4o-mini", temperature=0)

@summarize_with_llm(llm)
def run_report(region: str) -> dict:
    ...

Exactly one of model= / llm= must be provided.

Provide instructions to llm

Pass instructions to add task-specific guidance without rewriting the whole prompt template:

@summarize_with_llm(
    model="openai/gpt-4o-mini",
    instructions="Respond in French. Flag any premium below $1,000.",
)
def run_report(region: str) -> dict:
    ...

The text is merged into the prompt's system message on every call, so it composes with the default prompt — or with any custom prompt= you supply.

Return modes

• "summary": Return only LLM commentary (str).
• "original": Return only original function output.
• "tuple": Return (original_output, commentary).
• "dict": Return {value, commentary, info} (customizable keys).
• "object" (default): Return SummaryResult dataclass.

Routing with ActRouter

Point the decorator at a running ActRouter deployment and it will pick the model for you. ActRouter only ever receives the function's static metadata (name, signature, docstring, type hints, optional budgets) — never call arguments or return values.

from actdecor import summarize_with_llm

@summarize_with_llm(
    model="openai/gpt-4o-mini",                # initial / fallback model
    router_url="https://<your-actrouter>",     # ActRouter base URL
    router="heuristic",                        # routing strategy
    route_hints={"task_kind": "summarization", "cost_budget_usd": 0.05},
)
def summarize_article(text: str) -> str:
    """Summarize a news article in 3 bullet points."""
    ...

result = summarize_article(article_text)
print(result.info["routing"])
# {'model': 'gemini-2-5-flash', 'source': 'actrouter', 'applied': True, ...}

When the decorator uses model="provider/model", "applying" a routed model simply swaps the string used for subsequent completion() calls — no client mutation involved. When the legacy llm= path is used, apply_model_to_llm patches the runnable's model / model_name / model_id attribute (or calls set_model if present).

On the first call ActDecor:

1. detects which major LLM vendors are usable here and limits candidates to them;
2. looks the function up in the inventory file (a miss the first time);
3. calls POST /v1/route on ActRouter with the function metadata;
4. records the recommended chosen_model in the inventory file, keyed by a stable fingerprint of the function;
5. points the active LLM target at that model (a string swap for model=, or an attribute patch for llm=).

On every later call (including in a fresh process) it reads the model from the inventory file and skips the ActRouter round-trip.

The function inventory file

A plain JSON hash map of function fingerprint -> recommendation:

{
  "version": 1,
  "functions": {
    "9f1c2a3b4d5e6f70": {
      "function_name": "summarize_article",
      "qualname": "summarize_article",
      "module": "news.pipeline",
      "recommended_model": "gemini-2-5-flash",
      "router": "heuristic",
      "estimated_cost_usd": 0.0017,
      "estimated_latency_ms": 330,
      "updated_at": "2026-05-12T12:00:00+00:00"
    }
  }
}

• Default location: ./actdecor_inventory.json, overridable with the ACTDECOR_INVENTORY environment variable or the inventory= argument (a path or a FunctionInventory instance).
• You can commit the file, hand-edit it, or pre-populate it to pin a model without ever calling ActRouter.

Restricting to vendors you can actually use

Before routing, ActDecor figures out which major LLM vendors are usable from the current environment and tells ActRouter to only consider those vendors' models. By default a vendor counts as "available" when its API-key environment variable is set (OPENAI_API_KEY, ANTHROPIC_API_KEY, GOOGLE_API_KEY / GEMINI_API_KEY, DEEPSEEK_API_KEY, XAI_API_KEY, MISTRAL_API_KEY, COHERE_API_KEY, DASHSCOPE_API_KEY, MOONSHOT_API_KEY, ZHIPUAI_API_KEY, MINIMAX_API_KEY, NVIDIA_API_KEY, …). Set probe_vendors=True to also ping each vendor's /models endpoint and drop ones whose key is rejected.

@summarize_with_llm(
    model="openai/gpt-4o-mini",
    router_url="https://<your-actrouter>",
    probe_vendors=True,                 # actually call each vendor's API
    # vendors=["openai", "anthropic"],  # or pin the set explicitly
    # vendor_env={"meta": ["TOGETHER_API_KEY"]},  # extra key env vars
)
def summarize_article(text: str) -> str:
    """Summarize a news article in 3 bullet points."""
    ...

print(summarize_article("...").info["routing"]["available_vendors"])  # ['anthropic', 'openai']
print(summarize_article("...").info["routing"]["candidate_models"])    # ['gpt-5-mini', 'claude-haiku-4-5', ...]

The candidate ids are taken from ActRouter's GET /v1/models (filtered by vendor family), falling back to a built-in catalog snapshot if that call fails. If no vendor is detected, ActDecor sends no restriction and lets ActRouter pick from its full catalog. Set restrict_to_available_vendors=False to disable this entirely, or pass an explicit candidate_models=[...] to bypass detection.

You can also probe / map vendors directly:

from actdecor import detect_available_vendors, available_candidate_models, ActRouterClient

vendors = detect_available_vendors(probe=True)            # {'openai', 'anthropic'}
client = ActRouterClient("https://<your-actrouter>")
candidates = available_candidate_models(vendors, router_client=client)

You can also drive routing manually:

from actdecor import ActRouterClient, FunctionInventory

client = ActRouterClient("https://<your-actrouter>")
model = client.recommend_model(
    summarize_article,
    task_kind="summarization",
    candidate_models=candidates,
)

FunctionInventory().record(summarize_article, model, router="heuristic")

Decorator options

Argument	Default	Purpose
model	None	Unified-endpoint model id, e.g. "openai/gpt-4o-mini".
llm	None	Legacy: a LangChain-Core-style runnable. Exclusive with model=.
completion_params	None	Per-call kwargs forwarded to actllminfer.completion (e.g. temperature, max_tokens, tools).
instructions	None	Additional instruction added to prompt message template.
router_url	None	ActRouter base URL. Enables routing when set.
router_client	None	Pre-built ActRouterClient (overrides router_url).
router	"heuristic"	Strategy: heuristic | rules | random | smallest | largest.
route_top_k	3	How many ranked candidates to request.
candidate_models	None	Explicit whitelist of model ids (bypasses vendor detection).
route_hints	None	Extra static metadata (task_kind, tags, token estimates, latency_budget_ms, cost_budget_usd, privacy_tier).
auto_route	True	Master switch for routing + inventory lookups.
apply_model	True	Whether to point the active LLM target at the chosen model.
use_inventory	True	Whether to read/write the inventory file.
inventory	None	Inventory file path or FunctionInventory instance.
route_fail_silently	True	Swallow ActRouter errors and keep the original model.
restrict_to_available_vendors	True	Limit candidate models to vendors usable from this environment.
probe_vendors	False	Also ping each vendor's API (not just check env vars).
vendor_probe_timeout	3.0	Per-vendor probe timeout, seconds.
vendors	None	Explicit vendor/family set; skips auto-detection.
vendor_env	None	Extra {vendor: [ENV_VAR, ...]} mappings for key detection.

API

• summarize_with_llm(llm=None, *, model=None, **kwargs) — decorator factory.
• ActLLMFunctionSummarizer(llm=None, *, model=None, **kwargs) — decorator class.
• serialize_for_llm(value, max_chars=12000) — serialization helper.
• SummaryResult — dataclass response object.
• ActRouterClient(base_url, ...) — HTTP client for ActRouter (route, recommend_model, list_models).
• ActRouterError — raised when ActRouter is unreachable or errors.
• FunctionInventory(path=None) — JSON-backed function → model hash map.
• build_function_metadata(func, ...) — static, privacy-safe metadata for ActRouter.
• function_fingerprint(func) — stable inventory key for a function.
• apply_model_to_llm(llm, model) / read_model_from_llm(llm) — best-effort model setter/getter for legacy runnables.
• default_inventory_path() — resolves the default inventory file location.
• detect_available_vendors(*, probe=False, ...) — vendor/family names usable here.
• probe_vendor(vendor, *, api_key=None, ...) — does this vendor's API answer?
• available_candidate_models(vendors, *, catalog_models=None, router_client=None) — vendors → model ids.
• VENDOR_API_KEYS, FALLBACK_FAMILY_MODELS — the built-in vendor maps.
• completion, acompletion, embedding, aembedding, Router — re-exported from actllminfer for direct use.