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

Annotations already cover read-only, idempotent, non-destructive, closed-world behavior, so the description's job is additive — and it delivers: result ordering, the two-part composition of the list, and the critically important fact that preview_url links expire after 1 hour. It doesn't discuss pagination behavior beyond the limit parameter or whether media_url is permanent.

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 sentences with no filler; the result composition and ordering come first, followed by the actionable handoff and the URL-expiry caveat. Nothing is repeated from the schema or annotations.

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 carries the burden of describing returns and does so usefully — list ordering, the two segments, and two named fields (media_url, preview_url) with an expiry caveat. It leaves unclear whether there is pagination/cursor support or whether media_url persists, minor gaps for a one-parameter list tool.

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 limit parameter is already documented with range and default. The description adds nothing about limit, which is acceptable given the schema does the work, so the baseline 3 applies.

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The description enumerates exactly what the resource contains: unpublished images created/imported by the assistant, then images and videos from the person's posts, ordered newest first. That content scope implicitly separates it from list_posts or get_upload_result. It stops short of naming a sibling, so it lands at 4 rather than 5.

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?

"create_post accepts each media_url" gives a clear downstream use case that tells the agent why and when to call this. There is no explicit when-not guidance or pointer to the sibling that adds media (import_media_from_link) or fetches upload results, so the routing picture is only half complete.

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