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

Annotations already declare idempotent=true, destructive=false and openWorld=true; the description adds the genuinely useful fact that 'It stays in their library either way', clarifying the change is visibility-only and reversible rather than a delete. It does not discuss permission requirements or how the public page is re-rendered, which are minor given the annotation coverage.

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 short sentences, no filler, and the primary action with its boolean value is front-loaded. The second sentence adds only the non-obvious reassurance about library retention.

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 four fully documented parameters, rich annotations, and no output schema, the description covers what an agent needs: what changes, what persists, and implicitly the single-item scope. It could add one clause about what to do when a title is ambiguous, though the schema already directs agents to item_id.

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 description coverage is 100%, so media_type, title, item_id and hidden are all documented in the schema, including the item_id-over-title precedence rule. The description only reinforces the meaning of `hidden` in plain language; baseline 3 applies since the schema carries the load.

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 effect ('Leave one item off the user's public page') plus the inverse ('let it show again'), so the toggle semantics are unambiguous. It implicitly separates itself from set_favorite/set_priority by scoping to public-page visibility, but never names a sibling to confirm that distinction.

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?

'Leave one item off... (hidden = true), or let it show again (false)' implies both directions of use, and 'one item' signals this is the single-item path rather than a bulk operation. There is no explicit when-not guidance and no named alternative for multi-item changes, so usage remains inferred.

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