contextcounter 0.1.3

Universal context limits, token counting and tool callings for OpenAI, Anthropic, and Gemini.

📦 ContextCounter

ContextCounter is a lightweight Python library for:

• 🔍 Fetching context window limits across LLM providers (OpenAI, Anthropic, Gemini)
• 📊 Counting tokens in text or chat messages, with safe fallbacks
• ✅ Checking if you’re about to exceed context

It works out-of-the-box with no dependencies, and can optionally integrate with official SDKs for precise context sizes.

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🚀 Installation

pip install contextcounter

Optional extras (for better accuracy):

pip install "contextcounter[openai]"       # precise OpenAI context limits
pip install "contextcounter[anthropic]"    # precise Anthropic context limits
pip install "contextcounter[tokenizers]"   # local tokenizers (tiktoken, transformers)

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⚡ Quickstart

from contextcounter import ContextInspector

# create inspector bound to a provider (openai, anthropic, google/vertex)
ctx = ContextInspector(provider="openai")

# fetch context window for a model
limit = ctx.get_limit("gpt-4o")
print("Context window:", limit)

# count tokens in free text
tokens = ctx.count_text("Hello world", model="gpt-4o")
print("Tokens:", tokens)

# count tokens in a chat-style message list
messages = [
    {"role": "system", "content": "You are a helpful assistant."},
    {"role": "user", "content": "Summarize this in 5 points."},
]
msg_tokens = ctx.count_messages(messages, model="gpt-4o")
print("Message tokens:", msg_tokens)

# check if it will exceed
print("Will exceed?", ctx.will_exceed(msg_tokens, "gpt-4o", reserve=2048))

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📖 API Reference

ContextInspector

from contextcounter import ContextInspector

ctx = ContextInspector(provider="openai")

• provider: "openai" | "anthropic" | "google" | "vertex" | None
  • If given, you don’t need to repeat provider in every function.
• gemini_overrides (dict, optional): override documented Gemini limits (default is 1_000_000 tokens).

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ctx.get_limit(model: str) -> int | None

Returns the maximum context window for the given model.

• For OpenAI models: will query live API if openai package is installed & authenticated.
• For Anthropic: will query live API if anthropic package is installed & authenticated.
• For Gemini: uses documented defaults (1,000,000) unless overridden.
• Fallback: internal static defaults.

ctx = ContextInspector(provider="anthropic")
print(ctx.get_limit("claude-3-7-sonnet"))  # 200000

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ctx.count_text(text: str, model: str | None = None) -> int

Returns the number of tokens in a plain text string.

• Tries tiktoken if available (for OpenAI models).
• Falls back to GPT-2 tokenizer if transformers installed.
• Last resort: heuristic (≈1 token per ~3.7 characters).

print(ctx.count_text("Hello world", model="gpt-4o"))  # → 5 (approx.)

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ctx.count_messages(messages: list, model: str | None = None) -> int

Returns the number of tokens in a chat-style message list.

• Adds structural overhead tokens per message (default: 3 tokens, 6 for system role).
• Handles content as strings or lists (for multimodal formats).

messages = [
    {"role": "system", "content": "You are helpful."},
    {"role": "user", "content": "Tell me a joke."}
]
print(ctx.count_messages(messages, model="gpt-4o"))  # → ~20

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ctx.will_exceed(tokens: int, model: str, reserve: int = 1024) -> bool | None

Checks whether a given token count plus a reserve buffer will exceed the model’s context window.

• Returns True if it will exceed, False otherwise, None if limit unknown.

tokens = ctx.count_messages(messages, model="gpt-4o")
print(ctx.will_exceed(tokens, "gpt-4o", reserve=2048))

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Standalone Functions

If you don’t want to use the ContextInspector class, you can import the core functions:

from contextcounter import get_context_limit, count_text, count_messages

print(get_context_limit("gpt-4o", provider="openai"))
print(count_text("Hello", model="gpt-4o", provider="openai"))

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🔧 Supported Models & Defaults

Provider	Model Example	Context Limit (tokens)
OpenAI	gpt-4o, gpt-4.1	128,000
OpenAI	o3	200,000
Anthropic	claude-3-7-sonnet	200,000
Anthropic	claude-3-5-sonnet/haiku	200,000
Google	gemini-1.5-pro/flash	1,000,000

Live API calls (OpenAI, Anthropic) will override these defaults if you have SDKs installed + credentials configured.

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🧪 Testing

pytest tests/

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📌 Roadmap

• ✅ Token counting across providers
• ✅ Context limit retrieval with fallbacks
• 🔜 Native Gemini token counting (when tokenizer becomes public)
• 🔜 More granular overhead estimation per provider

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📄 License

MIT © Nemlig ADK