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

The destructiveHint=true annotation is backed up with concrete semantics: the call REPLACES the post's existing media, and the already-set cover is kept unless keep_cover: false is passed. It also discloses the cost profile ("Free") and that media is attached "exactly as it is" (no reprocessing), which goes meaningfully 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?

Front-loaded with the core action and accepted media shapes, then alternatives, then the cover caveat. Every clause carries information an agent needs; even the terse "Free." earns its place as a cost signal.

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 5-parameter mutation tool with no output schema, everything needed to call it correctly is present: id provenance, cardinality limits, ordering, replacement/destructive semantics, cover behavior, cost, and sibling routing. Nothing material is left to inference.

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 100%, so the baseline would be 3, but the description still adds derivable meaning: asset_ids order maps to carousel slide order, keep_cover's default-keep/clear-on-false behavior, and the provenance rule tying ids to list_brand_assets or list_creations. These are the two parameters most likely to be misused, and the description disambiguates both.

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 ("Attach the owner's OWN media from the brand Library to a planned post") and enumerates the exact accepted shapes: one picture, up to 10 as a carousel in order, or one video. It explicitly distinguishes itself from the two nearest siblings, attach_video_to_post and attach_visual_to_post, so an agent can route correctly without opening any schema.

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 explicit when-not guidance by naming alternatives and the condition that selects them ("For a Video Studio film use attach_video_to_post; for a just-generated visual, attach_visual_to_post"). It also tells the agent where the ids must come from (list_brand_assets for uploads, list_creations for finished creations), closing the main pre-call question.

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