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

With no annotations, the description must carry the full behavioral burden. It usefully discloses the ordering of results and the relationship between limit and start_channel_job's max_videos, plus the has_more signal. However, it does not state read-only safety, authentication needs, rate limits, or the full return shape beyond duration metadata, leaving gaps for a tool with zero annotation coverage.

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 sentences, front-loaded with the core action and ordering, then the limit/has_more relation. Every clause earns its place; 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?

For a two-parameter list tool with no output schema and no annotations, the description covers purpose, ordering, return signal (has_more), and a key cross-tool relation. It could be more complete by describing the return format beyond duration metadata or pagination behavior, but it is largely sufficient.

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 100%, so the schema already documents both parameters. The description adds value by linking limit to start_channel_job's max_videos, clarifying that limit=N limits the preview rather than the download. It doesn't expand on the channel parameter beyond the schema's 'Handle, name, or ID'.

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?

The description starts with a specific verb 'List' and resource 'a YouTube channel's videos', adds duration metadata and a precise ordering scheme (long-form, Shorts, livestreams; newest first). It also distinguishes itself from start_channel_job by framing limit as a preview. An agent can identify the tool's function 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?

It tells the agent this tool previews what start_channel_job with max_videos=N would download, and that has_more indicates more content exists. This provides clear context for when to use it as a pre-download check, though it does not explicitly list other alternatives like get_channel_info or state 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.