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

Annotations already carry the safety profile (destructiveHint=true, readOnlyHint=false), so the bar is lower, yet the description adds useful behavior: the dual set/remove mode via null, the fact that a clip's own poster is used, and the optional before_generation_id role. It does not state ownership/permission requirements or what happens to an existing cover when replaced, leaving a small gap.

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?

Purpose is front-loaded and each clause carries information (source type, removal mode, prerequisite, optional param). The first sentence is long and dense, but no sentence is wasted.

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, return values need not be described, and the description covers set/remove semantics, cover-source rules, and the optional diptych param. It omits auth/ownership requirements and behavior when the referenced generation isn't ready, which are minor for a 3-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 coverage is 0% and the raw schema has no property descriptions, so the description must compensate — and it does for two of three params: generation_id (image vs clip, poster fallback, null to remove) and before_generation_id (input half of a guided recipe's before/after diptych, optional). Only recipe_id is left undefined, though its meaning is self-evident.

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 ('Set') and resource ('a recipe's cover') with scope detail: cover comes from a ready generation, and removal is triggered by `generation_id: null`. The verb/resource pair plus the source distinction cleanly separates it from siblings like set_recipe_gallery and publish_recipe.

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?

Explains when to use it (once you have a ready generation to promote as cover) and states a concrete prerequisite — publish_recipe refuses a row without a cover — which gives an agent real context for calling it. It stops short of naming an explicit alternative tool or when-not-to-use it.

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