Custom AI agents vs agent platforms

Platforms win when

Your workflow fits their connectors and compliance story, and you accept their roadmap.

Custom wins when

You need deep integration, unusual documents, or audit behavior a product will not customize.

You already pay for engineering and own the operational risk.

Hybrid

Common: platform for commodity pieces, custom orchestration for the core case path.

Decision test

Map your workflow to the platform happy path. If you need three custom escape hatches on day one, price a custom loop honestly.

If the platform fits 80% and the last 20% is configuration, buy.

Exit criteria

Whether you buy or build, export rules, schemas, and case history. Avoid designs that trap operational knowledge in a vendor UI only.

In practice

Map the workflow on a whiteboard before you open a framework: inputs, systems of record, humans, and irreversible writes. If that map is fuzzy, the agent will encode the fuzz.

Pick ten to fifty real historical cases as an eval set. Include the ugly ones. Run the agent offline against them until critical fields and hard rules are acceptable. Only then connect write tools.

Ship with a pause switch, a human queue, and a weekly review of override reasons. Promote repeated overrides into rules. That loop is how production systems improve—not another prompt brainstorm.

Common failure modes

• Treating a demo on clean samples as readiness for production volume.
• One shared service account with broad write access across systems.
• No owner for the exception queue, so failures pile up as noise.
• Changing prompts and models without regression gates on real cases.
• Measuring only model latency or thumbs-up, not completed-case cost and audit completeness.

What good looks like after ninety days

The first workflow is boring: stable override rate, known failure modes, operators who trust the queue. Config changes go through review. Traces answer "what happened to this case?" without archaeology.

At that point you can add a second document type or a second agent role. Expanding before the first path is boring is how programs stall with five half-built pilots.