# You Should Write An Agent · The Fly Blog

<https://fly.io/blog/everyone-write-an-agent/>

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- Saved: November 11, 2025 (2025-11-11T14:17:04Z)
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## What Jamie wrote

Great article walking through creating an agent using Python and then extending it with tools and capabilities. It is all a pretty simple example, but it is powerful to show how much capability you can create with these. I think it is fair to say that today every developer should know how to author their own agents with sub-agents and tools. Compared to deploying something in AWS, this is easy.

The author correctly highlights what I know to be one of the biggest challenges — managing context windows.

> You're allotted a fixed number of tokens in any context window. Each input you feed in, each output you save, each tool you describe, and each tool output eats tokens (that is: takes up space in the array of strings you keep to pretend you're having a conversation with a stateless black box). Past a threshold, the whole system begins getting nondeterministically stupider. Fun!
> 
> No, really. Fun! You have so many options. Take "sub-agents". People make a huge deal out of Claude Code's sub-agents, but you can see now how trivial they are to implement: just a new context array, another `call` to the model. Give each `call`different tools. Make sub-agents talk to each other, summarize each other, collate and aggregate. Build tree structures out of them. Feed them back through the LLM to summarize them as a form of on-the-fly compression, whatever you like.
> 
> Your wackiest idea will probably (1) work and (2) take 30 minutes to code.

Great stuff.

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## Elsewhere

- Wayback Machine: https://web.archive.org/web/*/https://fly.io/blog/everyone-write-an-agent/