Langchain

What it does

When your agent uses it

• Creating tool-calling agents
• Switching model providers
• Adding structured output

Example prompts

• “/langchain”

Requirements

• Python 3
• Node.js
• Compatibility (from SKILL.md): Python 3.10+, Node.js 22+

Workflow steps

4 steps, taken from the first numbered list in SKILL.md.

1. 1Snake_case tool names—Tool function names must be valid Python identifiers. Use get_weather, not get-weather.
2. 2Reserved parameters—Do not name tool parameters type, name, or description as these conflict with the tool schema.
3. 3Provider packages—Models live in separate packages (e.g., langchain-openai). The base langchain package does not include providers.
4. 4Model string format—Use "provider:model-name" format with init_chat_model() (e.g., "openai:gpt-5.5").

What it can do on your machine

Read from SKILL.md and the folder at commit be3028f. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  Shell commands in SKILL.md call:

  • pip
  • npm

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  Hosts in commands or code, which the agent is likely to contact:

  • reference.langchain.com

  Also links to:

  • docs.langchain.com

  From URLs in SKILL.md, links to its own repository left out.

• Credentials

  Names no API keys, tokens, secrets or passwords.

  From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

• Compatibility

  Python 3.10+, Node.js 22+

  From compatibility in the SKILL.md frontmatter.

Context cost

Langchain loads about 1.1k tokens when it runs. Until then it costs about 47 tokens; SKILL.md has 301 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~47

When it runs · the whole SKILL.md, loaded when a task matches

~1.1k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from langchain-ai/docs at commit be3028f, republished under its MIT licence (© langchain-ai). 301 words, ~1,118 tokens.

name

langchain

description

Build agents with a prebuilt architecture and integrations for any model or tool. Use when creating tool-calling agents, switching model providers, or adding structured output.

compatibility

Python 3.10+, Node.js 22+

license

MIT

metadata.author

langchain-ai

metadata.version

1.0

# Python
pip install -U langchain

# JavaScript/TypeScript
npm install langchain @langchain/core

# Python
pip install -U langchain-openai       # or langchain-anthropic, langchain-google-genai

# JavaScript/TypeScript
npm install @langchain/openai         # or @langchain/anthropic, @langchain/google-genai

from langchain.agents import create_agent

def get_weather(city: str) -> str:
    """Get weather for a given city."""
    return f"It's always sunny in {city}!"

agent = create_agent(
    model="openai:gpt-5.5",
    tools=[get_weather],
    system_prompt="You are a helpful assistant",
)

result = agent.invoke(
    {"messages": [{"role": "user", "content": "What is the weather in SF?"}]}
)

from langchain.chat_models import init_chat_model

# Switch providers by changing the string
model = init_chat_model("openai:gpt-5.5")
model = init_chat_model("anthropic:claude-opus-4-8")
model = init_chat_model("google_genai:gemini-3.6-flash")

from langchain.tools import tool

@tool
def search(query: str) -> str:
    """Search the web for information."""
    return "search results"

© langchain-ai, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in src/.mintlify/skills/langchain of langchain-ai/docs.

Open the folder on GitHubat commit be3028f