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

Beyond the readOnlyHint/openWorldHint annotations, the description adds two pieces of genuinely useful behavior: cost ("Costs 1 credit on success") and sort order (newest first for channels). It doesn't discuss pagination or what happens when a channel has more than `limit` uploads, which keeps it off a 5.

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?

Three short sentences: capability and return fields first, then the routing guidance, then the cost note. Nothing is redundant with the schema and every sentence carries information an agent needs.

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 the description compensates by naming the returned fields, plus it discloses credit cost and ordering for a two-parameter read tool. The only gap is behavior around large results (pagination or truncation past `limit`), which is minor for a read-only list 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 the url and limit semantics are already documented in the schema, making 3 the baseline. The description implies that a channel input yields "recent uploads" while a playlist yields the full list, which adds a little meaning about how `limit` interacts with input type, but no format or edge-case detail beyond that.

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 ("List the videos ... of a YouTube playlist or channel") and even enumerates the returned fields (id, title, duration, URL), so an agent knows exactly what comes back. The playlist-vs-channel distinction and the "newest first for channels" ordering rule further separate it from get_transcript and get_video_metadata.

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 a clear routing rule: "Use it before get_transcript to work on a whole playlist or a channel's recent uploads." That names the sibling and the condition that selects this tool. It stops short of saying when to prefer get_video_metadata for a single video, so not a full 5.

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