Add a divider line

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

Annotations already declare that this is a non-read-only, non-idempotent, non-destructive open-world write. The description adds the behavior that matters most beyond that: where the divider is placed, how the default selection behaves, and how to reposition it afterward. The remaining gap is that it does not say whether repeated calls stack dividers at the end, which the idempotentHint=false annotation only hints at.

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?

Three short sentences, front-loaded with the action and followed by the placement rule and the follow-up route. There is no redundant restatement of the title or annotations, and every sentence adds usable information.

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 zero-parameter insertion tool with no output schema, the description covers what is inserted, where it goes, and how to move it later. The only gap is that it doesn't say whether the call returns a handle to the new section, which matters if the user wants to move or delete it without searching.

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 tool takes zero parameters, so no parameter prose is required; the baseline for a 0-param tool is 4. The description correctly does not invent parameters and instead explains the implicit placement state that the agent must control.

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 uses a specific verb and resource: 'Insert a horizontal divider line.' That is clearly distinguishable from the other gsites_add_* tools, which handle text, images, embeds, and layouts. It does not explicitly name a sibling it differs from, so it falls just 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?

It states the insertion context: the new divider goes after the currently selected section, and with the default selection it is appended at the end. It also redirects the agent to gsites_move_section for reordering. It never mentions gsites_set_insert_point, which is a sibling that likely controls where content lands, so the guidance is clear but not exhaustive.

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