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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered without the description. The description adds the gating rule about explicit user requests, but says nothing about cost, latency, model behavior, or what a 'description' contains. Adequate but not rich beyond the annotations.

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 short sentences with zero filler. The core action leads, the input source follows, and the invocation guard comes last, which is the right ordering for an agent scanning top-down.

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 single-parameter, read-only tool with no output schema, the definition covers action, input provenance, and the trigger condition. The only gap is that the shape of the returned description is not characterized, which is minor given the tool's simplicity and the readOnly annotations.

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 the single parameter is documented identically in both places ('Id returned by list_my_media or search_image_library'), so the description adds no meaning beyond the schema. Baseline 3 applies when the schema does the work.

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 a specific verb and resource: 'Describe one image of the media library.' It also names the two sibling tools that produce the required input (list_my_media, search_image_library), which helps an agent locate it among a large sibling set. It stops short of saying how it differs from those siblings beyond input provenance.

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?

Gives an explicit usage condition: 'Use it only when the user explicitly asks about an image,' plus the prerequisite for obtaining media_id. It does not name what to use instead when the user has not explicitly asked, so the exclusion is stated but the alternative path is left implicit.

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