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Composability: New Features Through New Prompts

The Idea

With atomic tools and parity in place, new features stop being code you write and become prompts you compose. Want a “weekly review” feature in a notes app? That’s just a prompt: “Review files modified this week. Summarize key changes. Based on incomplete items and approaching deadlines, suggest three priorities for next week.” The agent uses list_files, read_file, and its judgment. You described an outcome; the agent loops until it’s achieved.

Composability works for both developers and users. Developers ship new features by adding prompts. Users customize behavior by modifying prompts or creating their own. This collapses the gap between product team and end user — both are operating on the same surface.

The Constraint

Composability only holds if two conditions are met: tools must be atomic enough to compose in unanticipated ways, and the agent must have parity with what users can do. If tools encode too much logic, composition breaks down because each “tool” already presupposes a workflow. If parity is incomplete, prompts will silently fail at the missing capability.

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