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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is covered. The description adds genuinely useful context about what is computed and that the numbers mirror the editor, but it says nothing about failure modes (unsegmented job), whether thresholds are configurable, or cost of the computation.

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 sentences, zero filler, and the core content (what is measured) leads before the secondary note about the editor mirroring. Nothing could be removed without losing information.

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 no output schema, the description does a reasonable job of sketching the return payload (per-cue metrics plus over-limit cues), but omits the unit conventions, whether severity thresholds are exposed, and the preconditions for a valid job. Adequate, not complete.

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 100% with only two parameters, so the schema already explains jobId and the primary/secondary track enum. The description contributes no additional meaning about either parameter, which is exactly the baseline case.

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 definition names the exact metrics returned (per-cue reading speed, displayed length, characters-per-second) and adds the flagging behavior for cues exceeding limits, which separates it from lunara_list_cues and lunara_qa_contract. It is a noun phrase rather than an explicit verb+resource statement, and it never says the metrics are computed for a subtitle job's cues, but that is inferable from jobId and the sibling set.

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?

There is no when-to-use guidance at all: no mention of when readability checking should happen in the pipeline, no reference to lunara_list_cues, lunara_qa_contract or lunara_get_coverage as alternatives, and no prerequisites such as the job having been segmented or transcribed first.

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