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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), so the bar is lower; the description adds real behavioral context by enumerating the returned fields and clarifying that image_url is the photo or video cover frame and video_url is a downloadable mp4. It doesn't mention the default 25-item cap or pagination behavior.

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?

Purpose is front-loaded, followed by return-shape detail and a routing sentence; every clause carries information. No padding or restatement of the name.

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 2-parameter read tool with annotations covering safety and an output schema covering the return shape, the description adds the routing and provenance context an agent needs to call it and chain it 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 coverage is 0%, so the description carries the burden. It meaningfully explains page_id's provenance ('comes from list_meta_pages'), but says nothing about the limit parameter or its default of 25, leaving half the parameters unaddressed.

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 ('Lists a Facebook Page's recent posts and THEIR MEDIA') and even names the downstream goal (reuse as ad creative). It's clearly distinguishable from adjacent siblings like list_meta_instagram_posts and list_tiktok_posts.

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?

Explicit routing guidance: feed video_url into create_meta_video_ad, image_url into create_meta_link_ad, and page_id comes from list_meta_pages. It stops short of stating when NOT to use it (e.g., vs list_meta_instagram_posts for Instagram media), so no exclusions.

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