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

Annotations already declare idempotentHint, destructiveHint, readOnlyHint=false and openWorldHint=false, so safety is partly covered. The description still adds real value beyond them: it clarifies no scraping/analysis occurs, defines note overwrite semantics ('omitting it preserves an existing note'), names the return value savedVideoId and its consumer (delete_saved_reference), and rules out card attachment. It stops short of explaining what destructiveHint means here (e.g., overwriting a note) or any auth requirements.

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?

Four short sentences, front-loaded with the core action and scope, each adding distinct information (no-analysis caveat, note semantics, return value, non-attachment). No 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 3-param write tool with no output schema and no annotation-contradiction, the description covers the essential call semantics and even states the return value. Missing only peripheral details like permission requirements or error behavior, which is minor here.

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 0%, so the description must carry the load, and it does for two of three params: videoId is the required key ('by videoId'), and note's optionality and preserve-on-omit behavior are explained. brandId is only hinted at via 'this brand's', leaving its format/derivation implicit.

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 + scope ('Save an existing catalog video to this brand's reference library by videoId') and immediately distinguishes itself from analyze_catalog_video ('without scraping or generating analysis'). An agent can separate it from siblings like analyze_catalog_video and save_reference_by_url without opening either 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?

Implicitly routes the agent: 'by videoId' separates it from save_reference_by_url (URL-based) and 'Does not attach the video to a content card' rules out attach_content_reference. However, it never names those siblings explicitly or states a when-not condition, leaving some inference to the agent.

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