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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the description does not need to restate that. It adds value by noting the pagination behavior ('use cursor when paginated') and the exclusion of hashtag searches, which are useful behavioral details beyond the annotations.

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?

The description is two sentences, front-loading the core action (search by free-text keyword) and then adding the key differentiator and pagination note. There is zero redundancy; every clause serves a purpose.

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?

Given the tool has 8 parameters but full schema coverage, and no output schema, the description adequately covers the main behaviors: search scope, return type, pagination, and the hashtag exclusion. It doesn't elaborate on filters or sort options, but those are well-documented in the schema, so nothing critical is missing for an agent 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 description coverage is 100%, so the schema already documents all parameters including query, type, cursor, etc. The description only reinforces the 'free-text keyword' nature of the query parameter and the cursor usage, but adds no new semantic detail. With full schema coverage, a baseline score of 3 is appropriate.

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?

The description clearly states it searches YouTube videos, channels, and playlists by free-text keyword, and explicitly distinguishes itself from hashtag search by naming the sibling tool. It also specifies the return type (a list) and the pagination mechanism, making the tool's purpose unambiguous.

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 provides an explicit exclusion ('not hashtag') and directs users to the correct alternative (youtube.search.hashtag.list). It also mentions when to use the cursor for pagination, giving clear operational guidance. This fully addresses when to use this tool versus its siblings.

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