Get one media item

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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and non-destructive behavior, so the safety profile is covered. The description adds meaningful context beyond annotations: the returned fields and the important limitation that only app-uploaded media is accessible. This is useful behavioral disclosure, though it does not discuss error cases.

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 sentences deliver the core action, return contents, scope limitation, and the routing alternative with no wasted words. The most important information is front-loaded.

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 read-only single-item fetch with one required parameter and no output schema, this description is complete: it explains what is returned, the access boundary, and the correct alternative for other cases. The annotations cover idempotency and safety, so no critical call-time information is missing.

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 are already documented. The description reinforces that media_item_id is the lookup key and adds the return fields, but it does not add meaning to the account parameter beyond what the schema already 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 uses a specific verb ('Fetch') and resource ('a single media item by id'), and states the key returned fields: dimensions, creation time, and description. It also explicitly distinguishes itself from start_pick_session, which is the sibling for reaching non-app-uploaded library content.

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 clearly states when to use this tool (fetch one media item by id) and when not to ('To reach anything else in the user's library, use start_pick_session'). The scope boundary—only media uploaded by this app—gives an agent a concrete decision rule.

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