Dispatches from O'Reilly: The right amount of spec for agentic development

Summary

As software agents make implementation faster and cheaper, engineering difficulty shifts away from typing code toward defining correctness and verifying behavior reliably. Omitting specifications forces human reviewers into expensive correction loops, while overspecification clutters model context windows with stale prose and competing instructions. To find the optimal middle ground, teams must validate specifications before coding, using one agent to draft minimal constraints and another to attack ambiguities, hidden dependencies, and missing failure modes. Multi-agent architectures demand formal interface contracts, schemas, and executable checks because interpretive drift compounds rapidly across unbounded agent handoffs. Core Extreme Programming and Agile practices such as continuous integration, small release batches, and rapid feedback loops remain essential error-detection mechanisms during agentic development.

Takeaways

1. 1

   Overspecification degrades agent accuracy due to context rot and instruction drift caused by obsolete design prose competing with active code.

2. 2

   Specifications can be pre-validated before implementation by prompting one agent to draft minimal criteria and a second agent to probe for contradictions, missing failure modes, and untestable claims.

3. 3

   Multi-agent systems require explicit interface contracts, schemas, and executable acceptance tests to prevent compounding interpretive drift across agent boundaries.