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

Annotations already declare readOnlyHint/idempotentHint/non-destructive, and the description adds genuinely non-redundant behavior: a 50-item page cap, the exact fields returned (including privacy_status enum values), and that page_token comes from next_page_token and is null on the final page. That termination rule is the kind of detail that prevents an agent from looping on a last page.

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 tight sentences, front-loaded with what is listed and its cap, then return fields, then the cross-tool id note, then pagination. Nothing is padding.

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?

With no output schema, the description carries the return shape and does so by enumerating every field. Page size, pagination loop and cross-tool id usage are all covered, leaving nothing an agent needs in order to call it correctly.

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 two parameters are already documented; the description goes slightly beyond by tying page_token to next_page_token and stating it is null on the last page, which the schema alone does not convey. profile_id semantics are left entirely to the schema, which is acceptable at 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 the playlists on a connected YouTube channel') and is trivially distinguishable from the sibling mutations youtube_playlist_create/update/delete. An agent knows exactly what this returns 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?

The description supplies a concrete downstream use case: the returned playlist id is the playlist_id that post_publish takes under platforms.youtube, which tells the agent when to call this before publishing. It does not explicitly compare against alternatives (e.g., youtube_playlist_create or playlist listing done elsewhere), so no exclusions are stated.

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