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

Annotations already declare readOnlyHint and destructiveHint=false, so safety is covered; the description adds real behavioral context beyond them: default newest-first ordering, that transcripts come back in the same call, and the cap of 5 rows. It does not mention the credit cost of transcripts or the 12,000-character truncation, but those live in the schema.

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 sentences, front-loaded with the core listing behavior and platform acceptance, then edge behavior (tab/sort/query) and finally the transcripts option. Dense but every clause carries functional information; 'creator's items' is the only slightly loose phrasing.

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?

An output schema exists, so return values need no explanation, and annotations cover safety. The description covers multi-platform input, per-platform parameter applicability, and the optional transcript augmentation, which is sufficient for an agent to invoke it correctly. Only the sibling-routing for playlists and channel search is left to 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 description coverage is 100%, so the schema already explains tab, sort, query, limit and transcripts in detail (including enum behavior and edge cases). The description restates the roles compactly (tab picks videos/shorts/live, sort orders, query searches inside the channel) but adds only the cross-tool hint about row urls, which is the baseline-plus level for full coverage.

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 a creator's items, newest first by default') and enumerates the accepted channel identifier forms across YouTube, TikTok, and Instagram. It is easy to distinguish from get_transcript and list_playlist_videos, though the playlist/podcast split is only made in the schema's tab description, not in the description text itself.

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?

'To read what the videos say rather than only their titles, set transcripts to N' gives an explicit use condition and an alternative path (get_transcript for audio-only videos). It also flags the cross-tool flow ('Every row's url can be passed straight to get_transcript'). It does not state when to prefer this over list_channel_playlists or search_videos, which are siblings an agent must choose between.

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