Page 4 of 8~120 min topic

Agents in code

Measure whether the bounded research agent works

Page 4 turns “it ran” into executable checks for the bounded research agent over a fixture KB.

~15 min this pageEvaluation

1Learn the idea

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Make the metric executable

Translate the claim into assertions or a tiny eval harness. The metric to protect is: step count ≤ max; citation coverage; abstention on empty search. Always record the denominator (how many cases) beside any rate. A percentage without a denominator is marketing, not measurement.

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Run the checks

const parsed = OutputSchema.safeParse(raw);
if (!parsed.success) {
  throw new ContractError("invalid_output", parsed.error.issues.map(i => ({
    path: i.path.join("."), code: i.code
  })));
}
return parsed.data;

Expected evidence: The agent searches once, cites kb://returns, and stops before MAX_AGENT_STEPS.. A passing assertion proves only the behavior it names; broader usefulness still needs the chapter’s full limits.

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Say what the metric does not prove

Be explicit: beating the baseline (single-shot LLM answer without search) on this fixture does not prove behavior under infinite tool loop, or final answer with no citations after search. Label observations separately from conclusions so the next page inherits honest evidence about the bounded research agent.

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Lab notebook: denominator discipline

Compute step count ≤ max; citation coverage; abstention on empty search with the denominator written beside the rate every time. For this chapter, the evaluation set is intentionally tiny; that is allowed only if you say so in the evidence. Compare against single-shot LLM answer without search before celebrating.

Add one negative case aimed at infinite tool loop, or final answer with no citations after search. A suite with only happy cases cannot protect the bounded research agent when the characteristic failure appears in review.

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Worked judgment

If a check is expensive or flaky, shrink it until it is deterministic on fixture KB with 4 notes + max_steps=3. Flaky green builds teach the team to ignore gates. Record what this page does not prove so security-ops and mastery-ship inherit honest limits.

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Why this stage matters for the bounded research agent

At the evaluation stage for agents-in-code, the job is narrower than finishing a product demo. You are creating one progressive evidence piece about fixture KB with 4 notes + max_steps=3 that later pages inherit without redefining success. Keep that fixture small enough to inspect by hand, keep outputs copy-pasteable as text, and refuse to narrate this baseline as if it were a production SLA: single-shot LLM answer without search.

For this page specifically, success looks like metrics with explicit denominators and a negative case while still centering the user decision to search a local knowledge base then produce a cited answer within a step budget. If you cannot point to a file, command, or assertion that proves that for the bounded research agent, stay on this page instead of advancing.

Glossary: tool · Glossary: structured output · Cheatsheet: production ops signals

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Before you start

Why this matters

Write one independent check that would catch a fake pass for this lab. Prefer a check tied to step count ≤ max; citation coverage; abstention on empty search over a check that only asserts “no exception.”

In the wild

See how this idea shows up as a product and a company — then come back to the lesson. Skills transfer across vendors.

Check your understanding

Page assessment

Answer from memory. Completion is saved from this evidence, not from opening the next page.

1. Is the metric computed with an explicit denominator?
2. Does a failing gold case actually fail the harness?
3. Did you separate observations from conclusions?
4. What remains unproved after these checks?

All responses are required.