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

The annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so "Read only" is a restatement of structured data rather than added value. The one genuine behavioral detail is the daily scoping implied by "left today" (a quota that resets), but nothing is said about what happens at zero remaining or any rate limits.

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 short sentences, front-loaded with the return content, then the routing hint. The first sentence is slightly convoluted ("the next few scheduled article titles a preview can be rendered on") and "Read only" is redundant with the annotations, costing a point.

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 correctly carries the burden of explaining the return value, and it does so (count plus sample titles). Only the zero-quota / failure behavior is left unstated for a read-only check the agent is told to call unconditionally before another 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 100% and the single `site` parameter is fully documented in the schema, including its allowed value. The description's "for this site" merely echoes that, adding no format or constraint detail. Baseline 3 applies when the schema carries the load.

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 states precisely what the tool returns: the remaining daily preview allowance plus the next few scheduled article titles eligible for a preview. That is far more specific than the tool name alone and separates this from the broader get_* listing tools (list_articles, get_overview) an agent might otherwise reach for.

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?

"Call before preview_image_style" gives an explicit sequencing rule that answers the main when-to-use question. There is no when-not guidance or error-case exclusion (e.g. what to do if the allowance is zero), so it stops short of a 5.

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