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

Annotations already indicate non-read-only and non-destructive. The description adds that the tool re-renders from existing cover, keeps composition, sets new one, and counts against AI limit. This provides useful behavioral context beyond annotations.

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?

Three concise sentences: first explains the action, second states prerequisite, third lists additional requirements. Front-loaded with key purpose, no filler. Every sentence adds value.

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?

Given the tool's simplicity (2 params, no output schema), the description covers workflow (prerequisite, AI limit, host requirement). It is complete enough for an agent to use correctly. Could mention that a new cover is set each time, but that's implied.

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?

With 0% schema description coverage, the description partially compensates by naming event_id and providing example instructions ('make it warmer'). However, it lacks explicit details about instruction format and constraints beyond examples.

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 clearly states the action ('refine') and resource ('event cover'), explains how it works (re-renders from existing cover, keeps composition), and distinguishes from generate_event_cover by noting the prerequisite. It is specific and unambiguous.

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 description provides explicit when-to-use guidance: event must already have a cover (generate_event_cover first), counts against AI-image limit, requires host status. It implies when not to use (no cover). However, it does not directly compare to sibling tools like set_event_image.

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