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

Annotations already declare non-read-only, non-destructive, open-world, non-idempotent, so the safety bar is lower. The description adds real behavioral value beyond that: confirm=false means preview (so the agent knows the default call does not actually publish), page_id is REQUIRED, and ice_breakers replace the auto-fill when given.

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-loads the core action and card constraint, then moves into parameter specifics. It is dense and long but every clause carries actionable detail; the enum list is verbose but bounded by '...'.

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 explanation. For a 12-param, 6-required creation tool the description covers the genuinely tricky parts (card structure, image source choice, CTWA fields, preview mode), leaving only trivial params to the schema.

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?

With 0% schema description coverage, the description must carry the load and largely does: it documents the cards item shape and the one-image-source rule, lists cta_type values, and explains welcome_message, greeting, and ice_breakers (≤80 chars, up to 4). It is silent on name, message, status, adset_id, and account_id, but those are self-evident or supplied by the schema defaults.

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 ('Creates a Meta carousel ad') and immediately scopes it with '(2-10 cards)', which distinguishes it from the sibling create_meta_link_ad, create_meta_video_ad, and create_meta_dynamic_ad tools.

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?

It gives useful conditional guidance — leave cta_type EMPTY to auto-pick from the ad set's messaging destination, and use welcome_message/greeting/ice_breakers for Click-to-WhatsApp/Messenger/Instagram-DM carousels — but never states when to choose this tool over a sibling ad-creation tool or any prerequisites beyond page_id being required.

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