Tools and Context - Marvin

context supplies data to a task. tools supplies Python functions the model can choose to call.

import marvin

def stock_level(product: str) -> int:
    """Return the number of units in stock."""
    return {"notebook": 12, "pen": 30}[product]

count = marvin.run(
    "Check stock for the requested product",
    result_type=int,
    context={"product": "notebook"},
    tools=[stock_level],
)

Tool signatures define input types, and docstrings describe their purpose. Tool code runs in your Python process with its permissions. Expose functions whose side effects you intend to allow.

Reuse tools on an agent

import marvin

def add(a: int, b: int) -> int:
    """Add two integers."""
    return a + b

calculator = marvin.Agent(tools=[add])
answer = calculator.run("Use add to calculate 23 + 19", result_type=int)

Tools belong to agents or tasks. Assigning thread.tools does not make a tool available.

Context is prompt data

import marvin

summary = marvin.run(
    "Summarize the release notes in one sentence",
    context={"release_notes": "Fixed installation and preserved saved usage records."},
)

Context keys are not interpolated into instructions. Use an f-string if you need to build instructions in Python. To share earlier messages, use a thread.

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