Simon Willison built a browser-based image editor specifically for Slack emoji: 128x128 pixels, transparent background, no extra steps.
He did not write it himself. Fable built it via pull request 305 in his tools repo. The tool exists because Slack's own creation flow is friction, and this removes it.
The interesting read is not the tool but the workflow: an AI agent committing a functional, requirement-scoped utility directly to a public repo. Check the PR to see how the spec translated to code.
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