Get Cover Art Archive images for a release

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

Annotations already declare readOnlyHint, idempotentHint, and openWorldHint. The description adds meaningful behavior beyond those: it returns URLs, does not embed image bytes, and errors clearly when no art exists. This gives the agent expectations about side effects, return content, and failure mode without contradicting any annotation.

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?

Three tight sentences put the core purpose first, then the return behavior, error condition, and read-only nature. The source attribution at the end is brief and unobtrusive. Nothing is redundant or padded.

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 two parameters, rich annotations, and no output schema, the description covers what the agent needs: what the tool fetches, what it returns, what it does not return, error behavior, and data provenance. This is sufficient for correct selection and invocation.

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 the schema already documents mbid and entity with types, enums, patterns, and descriptions. The description reinforces that the entity can be release or release-group and that the MBID keys the cover art, but it does not add significant meaning beyond what the input schema provides. 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 opens with a specific verb and resource: 'Fetch Cover Art Archive image metadata for a release or release-group MBID.' It enumerates the concrete outputs (front/back URLs, thumbnails, image types), which clearly differentiates it from the lookup/search/browse siblings.

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 makes the intended use clear: you need a release or release-group MBID and you will get cover art metadata. It also warns that an error occurs when no art exists, which is a useful boundary condition. It does not explicitly name alternative tools or state when not to use it, but the resource is distinct enough that this is a minor gap.

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