Play mayor in SimCity through an API

From the linked report, you connect your own agent to a headless Micropolis city simulator, either through an MCP server or a REST API. You give it a short brief, for example a small city with reliable power and room to grow, and the agent plays mayor. The site reports 406 mayors, 1,902 cities assembled and about 28 million total population.

Agent or tool: Custom agent
Topic: Software Development
Reported on: Hacker News
Added: 2026-10-15

Why it matters

Coding agents are moving from autocomplete to doing whole tasks: reading a codebase, making a plan and changing many files. This case is a concrete example of where that works in practice. It is one of 106 sightings filed under Software Development on Agent Sightings (number 96 by interest), and one of 182 involving Custom agent.

How you could try it

Here is a reusable prompt, written by us in our own words, that captures the task. Paste it into your own agent or any similar agent and adjust the details to your situation.

In this repo, play mayor in SimCity through an API. Read relevant code, apply a minimal patch, run available checks, and summarize the diff. Stop before merge or deploy.

The prompt breaks down into 3 steps you can check as the agent works:

In this repo, play mayor in SimCity through an API.
Read relevant code, apply a minimal patch, run available checks, and summarize the diff.
Stop before merge or deploy.

Tip: Work on a fresh branch, ask for a plan before edits, and review the diff and test results before merging.

Source

Read the original first-hand account on Hacker News: https://news.ycombinator.com/item?id=46946593. Our summary is a paraphrase; details are in the source.

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