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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint, and destructiveHint=false, so the safety profile is covered. The description reinforces this ('server marks it read-only, so it runs straight away') and adds the useful return-field detail, though it does not mention error behavior or rate limits.

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 dense, front-loaded sentences. The return-field list is directly useful because there is no output schema, and the sibling reference is placed after the core purpose. Nothing is wasted.

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 no output schema, the description compensates by enumerating the return fields (title, URL, image sizes, mime type, etc.). Combined with complete schema coverage and rich annotations, an agent has everything needed to call this tool correctly.

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%; both the id and site_id parameters are documented directly in the schema. The description adds no parameter-specific syntax or constraints beyond what the schema already provides, so the 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?

States the specific action and resource: 'Returns full detail for one Media Library attachment.' It also enumerates the exact fields returned and explicitly frames itself as 'the single-item complement to list-media,' making it easy to distinguish from the sibling list tool.

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 phrase 'single-item complement to list-media' implies the intended workflow: use list-media to find IDs, then this tool to fetch full details for one attachment. It does not explicitly state when not to use it or name other alternatives such as search-images, but the usage context is clear.

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