Declaration and return discipline

Commands

Write AI functions with @command in ~7 minutes. Requires Python 3.10+ and pip install alloy-ai.

Declaration and return discipline

• The decorated function returns a prompt str.
• The decorator’s output parameter controls the command’s actual return type.

from alloy import command

@command                  # returns str
def text_gen(topic: str) -> str:
    return f"Write a one-liner about: {topic}"

@command(output=int)      # returns int
def number() -> str:
    return "Return 6*7 as a number."

Why this shape: predictable typing in Python, explicit control of the model result type, and clear error surfaces when the provider cannot produce the requested type.

Sync, async, and streaming

Use sync or async functions. Both expose .async_() and .stream() helpers.

from alloy import command

@command(output=str)
def gen() -> str:
    return "Write a haiku about alloy."

print(gen())                  # sync
print(await gen.async_())     # async invocation of sync command

@command(output=str)
async def agen() -> str:
    return "Write a haiku about alloy."

print(await agen())

for chunk in gen.stream():
    print(chunk, end="")

async for chunk in agen.stream():
    print(chunk, end="")

Streaming policy (canonical): see Guide → Streaming.

Error surfaces and retries

• CommandError: model didn’t produce a final output or failed to parse into the requested type.
• ConfigurationError: invalid output shape or unsupported strict schema.
• Retries: configure(retry=...) or per‑call override.

from alloy import command, configure, CommandError

configure(retry=2)

@command(output=int)
def maybe() -> str:
    return "Return an integer between 1 and 10."

try:
    print(maybe())
except CommandError as e:
    print("Model error:", e)

Tools and contracts

Attach tools to a command to use your local capabilities. See Guide → Tools & Workflows and Guide → Contracts.