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

Annotations already cover safety (readOnly, idempotent, non-destructive, openWorld), so the bar is lower. The description still adds real behavioral context: results are query-scoped rather than platform-wide, and the view-count + upload-window combination is only an approximation of trending. It omits rate-limit and pagination behavior.

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 sentences, front-loaded with the core action before the trending nuance and payload-reduction note. Each sentence contributes, though the final sentence is the weakest and slightly tacked-on.

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 7-parameter read-only search with no output schema, the description plus fully documented schema and annotations cover what an agent needs to invoke it, including pagination via the documented cursor. It stops short of describing result volume or ordering defaults beyond 'relevance (default)' in 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 coverage is 100%, so the baseline is 3. The description goes beyond the schema by explaining the semantic interplay of `order` and `published` (trending equivalence) and the purpose of projection_preset/data_fields/item_fields (payload reduction), adding meaning the schema's per-field descriptions do not convey.

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 concrete verb+resource: 'Searches public YouTube videos', and clarifies the scope is query-based rather than platform-wide. It does not explicitly differentiate itself from nearby siblings like youtube_get_tag_videos or youtube_get_search_typeahead, which would have pushed this to a 5.

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 offers an implied usage pattern: emulate a trending chart via `order`=views combined with `published`. However, it never states when to prefer this tool over the tag-search or typeahead siblings, nor any prerequisites (auth, quota). Usage is inferable but not spelled out.

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