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

Annotations already declare readOnlyHint=false, destructiveHint=false, and openWorldHint=false, so the agent knows this is a safe, non-destructive local write. The description adds only the API mapping ('Mirrors POST /api/v1/folders') and says nothing about duplicate-name behavior, ownership requirements, or what the call returns.

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 with zero filler, and the core action is front-loaded. The optional nesting behavior and API mapping follow in the natural order of importance.

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 simple two-parameter create with annotations covering the safety profile, the essentials are present. However, with no output schema, the description gives no hint of what a successful call returns (e.g., the new folder ID), which an agent would need to chain into subsequent calls.

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 both 'name' and 'parent_id' are fully documented in the schema, including the ownership note and the null-for-root behavior. The description adds no syntax or constraint detail beyond what the schema already provides, so the baseline 3 applies.

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 ('Create a media library folder'), scoping it to the media library rather than generic folders. It implicitly distinguishes itself from siblings like create_tag and create_stream by naming the resource, though it never contrasts itself with related folder tools such as update_folder or move_files_to_folder.

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?

'Optionally inside a parent folder' is the only usage signal, and it simply restates the parent_id parameter. There is no guidance on when to create a folder versus using an existing one, no mention of permissions or prerequisites, and no routing to alternatives.

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