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

Goes well beyond annotations by disclosing that the call costs no credits, that it returns the whole board plus the new card, and by spelling out the exact auth mechanics (OAuth host prompt or 'Authorization: Bearer acd_live_…' header with the settings URL). These are behavioral facts an agent cannot derive from the readOnly/idempotent/destructive hints.

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 action and composition, then cost/return, then auth. Three sentences, each carrying distinct information with no redundancy.

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?

An output schema exists, so return values need no elaboration, and the description still summarizes them usefully. Auth, cost, and composition semantics are all covered, leaving nothing an agent needs 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 each parameter already names where its value comes from (list_saved_ads, list_canvases, revision semantics). The description adds no syntax or format detail beyond the schema, so 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?

States a specific verb+resource ('place a saved competitor ad on a board as a media card') and details exactly what is composed onto the card (video/image, advertiser as title, hook as caption, decoded brief attached). This clearly distinguishes it from generic siblings like add_media_card or add_generation_card, which have no competitor-ad origin.

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?

Usage is implied well by 'a saved competitor ad' and the requirement that the ad come from list_saved_ads/save_competitor_ad (per schema). It also notes the 'when it has one' conditional for the brief. However, it never explicitly names an alternative (e.g. add_media_card for non-ad media) or states when not to use it.

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