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

Adds real behavior beyond the annotations: the operation costs no credits, it returns the whole board plus the new card, and it details the two auth paths (OAuth host prompt or an 'Authorization: Bearer acd_live_…' header created in settings). Annotations only cover read-only/idempotent/destructive flags, so this auth and cost context is genuinely additive.

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 input constraint before the cost, return, and auth sentences. The auth/sign-in block is long, but it is operational information an agent needs rather than filler.

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 10-parameter tool with nested objects, an output schema, and 90% schema coverage, the description supplies the missing pieces: cost, return shape, and authentication. Nothing critical is absent, though the revision/position defaults are only covered in 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?

Schema coverage is already 90%, so the schema carries most parameter detail. The description still adds value by enumerating URL provenance ('import_asset result', 'generation's video_url', 'ad's video_url'), which maps to the enum values of the nested source.kind field (upload/generation/ad/studio) that the schema leaves unexplained.

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 ('Add an image or video card to a board') and immediately bounds the input ('from a public https URL'), which distinguishes it from add_text_card, add_frame, and add_generation_card.

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 clear context for when this applies by naming where the URL typically comes from (an import_asset result, a finished generation's video_url, an ad's video_url). It does not explicitly say when to prefer add_generation_card or ad_to_canvas_card over this tool, so the routing against those siblings is left implicit.

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