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

The description adds behavioral details beyond annotations: allowed formats (png/jpeg/webp/gif), size limit (≤10 MB), and the constraint that truncated payloads are rejected. It also implies the event must be live and the user must be a host. This complements the readOnlyHint=false and idempotentHint=true 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?

The description is a single dense paragraph that front-loads the purpose, then covers alternatives, constraints, and usage hints. It is reasonably concise with no wasted words, though it could be slightly more structured (e.g., bullet points).

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?

The description covers inputs and constraints well but does not explain what happens after setting the image (e.g., return value, success/error indicators). Given no output schema, this omission reduces completeness. Also, the openWorldHint suggests side effects not described, but the description covers the main behavior.

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?

The description explains image_base64 and image_url well, including that they are mutually exclusive and the meaning of each, plus format/size constraints. However, it does not mention the content_type parameter, which is in the schema but undocumented. Since schema coverage is 0%, the description partially compensates but misses one parameter.

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 tool sets or replaces a live event's cover image, specifying verb and resource. It distinguishes from sibling tools like set_event_address or set_event_url by focusing on the cover image, and mentions 'live event' for context.

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 explicitly instructs to provide one of image_base64 or image_url, and gives practical guidance on when to use each (if runtime can't move full bytes, use URL). It also notes requirements (event_id required, must be host). However, it doesn't compare to other tools or state when not to use this tool.

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