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

Annotations already declare readOnlyHint=false, idempotentHint=false and openWorldHint=true, so the description needn't re-explain safety. It adds nothing beyond that — no mention that each call produces a new non-deterministic output, whether credits are consumed (a credits_balance sibling exists), or how the 'video' case differs. The one added sentence is confusing rather than informative.

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 purpose is front-loaded in the first clause, which is good, but the remaining text is a run-on with stray line breaks and a second, semi-coherent instruction about video that does not earn its place. Roughly half the content is useful.

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?

An output schema exists, so return values needn't be described, but the single undocumented required parameter and the confusing video clause leave real gaps for an agent deciding when and how to call this generator. The annotation set carries the safety profile, yet the operational guidance is incomplete.

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 a single required 'prompt' parameter with 0% schema description coverage, so the description must explain what the prompt should contain and the description says nothing about it. The image-vs-video sentence introduces ambiguity about whether the prompt is for an image or a video.

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 verb+resource is clear ('Generate image to use in a post'), but the trailing clause about 'ask if they want to generate a picture of a video' muddies what the tool produces and blurs the line with the sibling generateVideoTool. An agent can identify the basic action but not confidently distinguish image output from the video alternatives.

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?

It does name a concrete trigger condition: use when the target platform requires an attachment and none was supplied. However, it never references the obvious alternatives (generateVideoTool, generateVideoOptions, uploadFromUrlTool) that an agent should weigh before generating, and the final instruction is ambiguous.

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