# Choose a model for each task

Separate planning, execution and review. Compare the total cost of a usable result.

## 1. Split the work

Planning and formatting a hundred records have different demands. Describe the input, output and cost of an error for each task. Use strong reasoning for difficult choices when your test justifies it. Simple, checkable work is a candidate for a cheaper model. Treat this as a hypothesis, not a universal ranking.

Choose one planning question, one formatting task and one review task.

## 2. Set the quality threshold first

Define a valid result before seeing model responses. For formatting, check required fields and counts. For a plan, specify constraints and unresolved decisions. A second model can help review, but use a check outside the model when possible.

Write three acceptance criteria per task and prepare a small test input.

## 3. Compare the same task

Give both models identical input and the same output contract. Record the result, duration, failure type and repair work. Start with a small fixed test set. A cheaper response requiring three repair attempts can cost more than an initially usable response from a more expensive model.

Save both outputs and assess them before looking at the model name.

## 4. Measure cost per usable result

Include model calls, retries and paid tool usage. Record human correction time separately. Use current provider billing; this guide promises no fixed savings percentage. Choose the cheapest model that passes your threshold and keep failure cases for the next test.

Fill the routing card: task, result, cost, repair work and chosen model.

## 5. Make fallback explicit

Failover after a provider error differs from escalation after a poor answer. Write separate rules. OpenRouter supports model fallbacks for certain error conditions; that does not replace your own quality review. Do not silently route confidential input to another provider. Test failure handling with test data.

Done when every task has a chosen route and a stop or fallback rule.

## Starter template

Create a routing card for these three tasks. Use only the models and prices I supply. Define acceptance criteria first. Compare the supplied outputs on quality, retries, cost and repair work. Recommend a model per task, with separate rules for provider errors and inadequate output. Mark missing numbers unknown.


# Model test card
Task: [one recurring task]
Fixed input: [file and version]
Valid result: [three testable requirements]

| Trial | Model | Valid? | Errors | Cost | Duration |
| A1 | [model A] | [yes/no] | [specific] | [actual] | [actual] |
| A2 | [model A] | [yes/no] | [specific] | [actual] | [actual] |
| B1 | [model B] | [yes/no] | [specific] | [actual] | [actual] |
| B2 | [model B] | [yes/no] | [specific] | [actual] | [actual] |

Cost per valid result = total trial cost / valid results.
Zero valid results means unusable output; do not divide by zero.
Primary route: [model and reason]
Technical-error fallback: [model and error condition]
Content uncertainty: [human review]