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

Annotations already indicate readOnlyHint and openWorldHint, and the description adds substantial behavioral detail: it searches only written text, never spoken content; it is retrieval, not ranking; it supports pagination via an offset; and it reads the connected channel directly without requiring user input. Nothing contradicts 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 long but front-loaded with the core purpose and heavily uses concrete examples. It is organized logically: purpose, triggers, single-record lookup, pagination, scope limits, alternatives, and invocation guidance. A few clauses repeat the same idea ('Needs no input' and 'Never ask the creator anything first'), so minor trimming would improve it.

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?

Because there is no output schema, the description compensates by explaining what results contain (match count and next offset) and how to paginate through a large catalogue. It also covers one-record retrieval, whole-library browsing, search limitations, and sibling tool routing, leaving an agent with enough context to invoke 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 88%, so most parameters are already documented. The description adds operation-level meaning for `video` (returns a single full record), `offset` (continue to the next page), and the empty-query browser behavior with newest-first ordering. The `title` parameter remains undocumented both in the schema and prose, keeping this from a perfect score.

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 first sentence states a specific verb and resource: 'SEARCH the signed-in user's own YouTube catalogue and LIST the videos that match' by titles, descriptions, and tags. It also explicitly contrasts with analyze_video and find_best_videos, making the tool's retrieval purpose unmistakable.

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 gives explicit when-to-use triggers ('call it whenever the user wants to FIND or LIST videos rather than judge them') plus concrete example queries. It also names alternatives for related but different tasks: analyze_video for performance and find_best_videos for best performers.

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