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

Annotations already declare readOnlyHint=false, destructiveHint=false, and idempotentHint=true, so the safety profile is covered structurally. The description's contribution is limited to confirming the target is an existing single folder (no creation, no media renaming). It says nothing about name-collision behavior, failure when folderId is unknown, or permission requirements, which are the remaining behavioral gaps for a rename mutation.

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?

A single front-loaded sentence with no filler, and the key constraint (one existing folder) comes first. Its brevity borders on under-specification rather than verbosity, so it loses a point only marginally.

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 two-parameter mutation with no output schema, annotations cover the safety profile, so the essentials are available. However, with zero schema description coverage the description should carry the parameter meaning and at least note the outcome (e.g., returns the updated folder, error on unknown folderId), and it does neither.

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 0%, so neither folderId nor name is documented in the schema. The description only weakly implies the mapping (folder = folderId, new name = name); it does not state whether folderId is an ID or path, whether name is the full new name or a suffix, or what the 120-character limit means.

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 names a specific verb ("Changes the name") and resource ("one existing library folder"), which clearly separates it from create_folder, remove_folder, and rename_media. It stops short of explicitly naming those siblings, so an agent must infer the boundary from the resource noun alone.

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 statement of when to use this tool versus move_media, remove_folder, or rename_media, and no prerequisites (e.g., folder must exist, ownership/permission requirements). The only implied guidance is "one existing folder", which is scope rather than routing guidance.

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