Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already carry the safety profile (readOnly, idempotent, non-destructive, closed-world), and 'deterministically replays' reinforces idempotency. The description earns credit by adding a genuinely non-obvious behavioral caveat: passing only validates software consistency and examples stay unpublishable until independent scan adjudication and review.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two tight sentences with the core action front-loaded and the caveat second, no filler. The dense comparison clause carries real information rather than padding.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With an output schema present the description needn't explain return shape, and annotations cover safety. It supplies purpose plus the crucial interpretation of a pass result; the only substantive gap is parameter documentation, which is a moderate omission for a two-param tool.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0% for two parameters, so the description must compensate and largely does not. 'Lists' faintly implies a limit-style paging behavior and 'local book-rule fixture' loosely gestures at fixtureId, but neither parameter's meaning, format, or defaults are explained.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description gives a specific verb+resource ('Lists or deterministically replays a local book-rule fixture') and even names the compared artifacts (expected matches, exceptions, source locators), so the agent understands the operation. It does not, however, distinguish itself from nearby siblings like validate_rule_spec or list_rule_review_queue.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Usage is only implied: the closing line clarifies that a pass means software consistency, not publishability, which hints at where this fits in a workflow. But it never states when to choose this tool over validate_rule_spec or the review-queue tools, nor any prerequisites for a fixture.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.