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

Annotations already flag a mutating, destructive, open-world operation. The description adds the create-vs-update discrimination but says nothing about what an update actually does to existing cards (full replacement? partial merge?), which is the main risk implied by destructiveHint=true. It also omits any authorization or publishing nuance the schema doesn't already contain.

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 short sentences, front-loaded with the resource and platform, then the create/update rule. Zero filler; every clause carries information.

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?

No output schema exists, and for a 7-parameter mutation tool the schema covers the field-level detail well. The description supplies the operational split and platform limit; the only meaningful omission is the semantics of updating (what gets overwritten) for a destructive operation.

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%, so all seven parameters, the enum CTA list, the 2-6 card bound and the distinct-image rule are already documented. The description merely restates the `id` semantics from the schema, adding no format or value guidance beyond it. 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 pair and resource ('create or update a CAROUSEL ad'), names the platform constraint (Reddit only), and the sibling names (create_update_image_ad, create_update_convo_ad, etc.) are distinguished by the 'carousel' qualifier. An agent can select it without opening the 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?

Explicit branching rule: include `id` to update, omit to create. That is the key fork for this tool. It does not name an alternative tool (e.g., upload_image_creative for card images, get_ad_details to fetch an existing id), so it falls short of the 5 bar.

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