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

Goes well beyond annotations: it discloses that the render reuses the existing cover and preserves composition, that a prior cover is mandatory, that the call consumes the monthly AI-image limit, and that a connected account is needed. Annotations only give the generic non-destructive/non-idempotent profile.

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?

Front-loads the core action and example instructions, then prerequisites and modes. Dense but every clause earns its place; the long em-dash sentences are slightly heavy but not wasteful.

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 4-param mutation tool with no output schema and no annotation depth, the description covers action, prerequisite, both ID modes, quota, and auth. Nothing an agent needs to invoke it correctly is missing.

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%, so the description must carry the load — and it does, explaining the event_id (live hosted event) vs draft_id+edit_token (unclaimed draft) relationship and giving example instructions. It stops short of documenting edit_token source or draft_id/event_id being mutually exclusive.

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+resource ('Refine the event's CURRENT cover') and clarifies the transformation mechanism ('we re-render from the existing cover, keep the composition'). It is clearly differentiable from generate_event_cover, which it names, and from set_event_image.

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?

Explicit preconditions and alternatives: 'There must already be a cover (generate_event_cover first)', and it spells out the two operating modes (live event you host vs unclaimed draft with edit_token). It also states the quota impact and the connected-account requirement.

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