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

Annotations declare readOnlyHint=false with destructiveHint=false and openWorldHint=false, so the description usefully adds the non-obvious prerequisites: an API key and a free StartupHub.ai account. It also discloses the return shape (markdown and image_url), which the absent output schema leaves undocumented. It does not mention credit cost or rate limits, so not a full 5.

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?

Five short sentences, front-loaded with the core action and then the required inputs, return values, and prerequisites. Tight and scannable. The two trailing auth sentences ('Requires an API key. Needs a free account.') are slightly redundant with each other.

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 covers return values (markdown, image_url) and prerequisites, which are the main things an agent would otherwise lack. Two optional parameters go unmentioned, but they are self-explanatory enough that this is close to complete.

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 50%, and the description adds real value by clarifying content_html accepts 'HTML or the article text' rather than just HTML. However, it names only title and content_html, leaving excerpt and source_url unaddressed in both description and schema. Baseline 3 fits.

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 and resource: 'Build a diagram and a short summary from an article.' An agent immediately knows this generates visual+text summary output. It does not explicitly distinguish itself from siblings like generate_article_video or humanize_text, which also transform text, so it stops short of a 5.

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?

Usage is implied by the input requirement ('from an article'), but there is no explicit when-to-use, when-not, or named alternative among the many generate_* siblings. The agent is left to infer that this is the tool for turning an article into a diagram plus summary.

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