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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the closing 'Changes nothing.' is largely redundant reinforcement. The description does add a modest behavioral fact by naming the fields returned (id/name, id/URL/date), but does not cover limits, ordering, or edge cases beyond that.

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 tight sentences: first the inventory of what is returned, then how to consume the ids, then the safety note. No waste and the key content is front-loaded.

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 compensates by enumerating the returned fields (character id/name; image id/URL/date). Combined with the downstream id-usage guidance, an agent has everything needed to call this and use its output.

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?

There is exactly one parameter (image_limit) and schema description coverage is 100%, including its default of 10 and 0-30 range, so the schema fully carries the semantics. The description never mentions image_limit or how it affects the result, so it adds nothing beyond the schema — the baseline 3.

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?

Specific verb+resource ('Lists your saved characters... and your most recent saved images') with the exact fields returned called out. It is clearly distinguishable from every sibling, all of which are generation, upload, or mutation tools.

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 tells the agent how the returned ids feed into downstream tools ('Use a character id for generate_video character_id or compose_scene character_ids, and an image id for compose_scene atmosphere_id'), which is strong contextual routing. It stops short of stating when not to use it or any prerequisite conditions, so it falls 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.