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

Annotations already declare readOnlyHint=false, idempotentHint=false, and destructiveHint=false, so the mutation profile is covered. The description adds genuinely useful context beyond that: the 8-folders-per-owner cap and the fact that the response returns the whole updated library. It stops short of stating permission requirements or what happens on hitting the cap.

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 with zero waste, front-loading the core action and following with the two constraints an agent actually needs. Nothing could be cut without losing 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?

With only one parameter, full schema coverage, and no output schema, the description supplies what is missing: the creation limit and the fact that the response contains the full updated library, removing the need for a follow-up read. It omits only edge-case behavior when the limit is exceeded.

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% and the single parameter already documents the 40-character limit, so the schema carries the load. The description adds nothing about the name parameter (e.g. uniqueness rules), making the baseline 3 appropriate.

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 states a specific verb and resource ("Creates a personal folder") and even disambiguates the terminology by mapping folder to category. However, it does not distinguish this from the sibling create_group, which an agent could easily confuse with folder/category creation.

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?

There is no explicit when-to-use guidance and no comparison to alternatives such as create_group or get_library. The mention of GET /api/library tells the agent what NOT to call afterward, but that is a return-value note, not selection guidance.

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