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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds two genuinely useful facts not in structured data: results carry “full stats” and each call costs 2 credits, which is real cost context for an agent. It says nothing about pagination behavior or rate limits, though the cursor parameter implies paging.

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 clauses, front-loaded with the action and resource, zero filler. The parenthetical credit note is compact and useful. “Full stats” is slightly vague but does not waste much space.

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 search tool with no output schema, the description gives only “full stats” as a hint about the return shape, leaving the response structure largely unexplained. Parameters and annotations are fully covered elsewhere, so the gaps are limited to return-value and paging expectations.

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%, with every parameter documented including the enum meanings and the RFC 3339 example, so the schema does the heavy lifting and the baseline of 3 applies. The description adds nothing about parameter usage, such as when to supply cursor versus how sort_by interacts with published_after.

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 ("Search YouTube videos") plus a scope hint in "full stats," which distinguishes it from lookups like youtube_video. It does not, however, differentiate itself from nearby search siblings such as youtube_search_hashtag or youtube_search_typeahead, so an agent must infer that this is the keyword/content search.

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?

There is no explicit when-to-use or when-not-to-use guidance, and no alternative is named. The agent can infer from the name alone that this is the keyword search, but nothing in the description confirms or excludes cases like hashtag search or channel search.

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