upload_playlist_cover

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

With no annotations, the description carries the burden of behavioral disclosure. It adds the scope requirement and the 403 error, which is valuable. However, it does not mention success behavior, reversibility, or idempotency, leaving some behavioral traits undisclosed.

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?

The description is a single efficient sentence that front-loads the action and then provides the critical scope requirement. No filler or redundant phrasing.

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 mutation tool without an output schema, the description covers the main operational detail (scope requirement) and failure mode. It is reasonably complete, though it could mention that the playlist must exist or that the cover replaces the existing one, but these are minor gaps.

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 both parameters already have descriptions in the schema. The tool description adds no extra meaning beyond implicitly noting the JPEG format, which is already covered by the schema. Baseline 3 is 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 clear verb ('Replace') and resource ('a playlist's cover image') with the method (base64-encoded JPEG). It is distinguishable from the sibling get_playlist_cover by implying the write operation, though it does not explicitly name that sibling.

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?

The description provides a concrete prerequisite (ugc-image-upload scope plus playlist-modify-public/private) and a failure condition (403 without it). This gives clear usage context, though it does not discuss alternatives or contrast with other playlist tools.

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