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

Annotations already establish the full safety profile (readOnlyHint=true, idempotentHint=true, destructiveHint=false, openWorldHint=false). The description adds genuinely useful behavioral content by stating the response surfaces step and stage matches plus unmatched rules, but it stops short of describing the preview's shape or its bearing on a subsequent apply.

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?

A single front-loaded sentence with no filler; the verb and scope arrive immediately. It is efficient, though its brevity is achieved partly by omitting needed detail rather than by tight editing.

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?

For a tool with five parameters at 0% schema coverage, nested objects, and no output schema, the description is thin: it never explains the preview payload, the effect of 'matches', or how the result feeds the apply step. An agent can guess it is safe and non-mutating from annotations but cannot confidently construct a correct call or interpret the result.

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% across 5 parameters, including a nested 'source' object and a nested 'matches' object, so the description carries the full documentation burden. It only obliquely hints at the concept behind 'matches' ('step and stage matches and unmatched rules') and says nothing about job_id, source.type/id, request_id, or source_digest, leaving the required source discriminator (starter vs job) unexplained.

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?

States a specific verb (preview copying) and resource (a starter's or job's rules), which is far better than a tautology. It does not, however, name or contrast itself with the obvious sibling yardstick_automation_starters_apply (or the rules_copy/preview family), so the agent must infer the preview-vs-apply relationship from the name alone.

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?

The word 'Preview' implies this is the non-mutating dry-run that precedes an apply, but the description never states when to use it versus yardstick_automation_starters_apply or which situation (template vs. existing job) calls for a preview. Usage is only implied, not instructed.

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