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

Annotations already declare readOnlyHint=true, openWorldHint=true and destructiveHint=false, so safety is covered. The description adds two genuinely new traits: the cost ('5 prepaid credits per successful call') and the shape of the returned transcript JSON (text, start, duration). The only weakness is the unsupported transcript-by-ID behavior claim.

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?

Front-loaded and dense, but the unsupported transcript-by-ID clause is noise, and the trailing 'This tool selects YouTube search.' is a redundant, grammatically odd sentence that earns no place. Removing both would sharpen the definition without losing information.

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 read-only, 4-param search tool with no output schema, the description does supply return shape and pricing, which is good. But it leaves a real ambiguity about whether transcripts are retrievable here versus via youtube_transcript, which matters for calling the right tool.

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% and both enums are documented in-schema, so the schema carries parameter meaning. The description adds no syntax or format detail for query/country/language/results, and its 'by video ID' phrasing introduces confusion rather than meaning about the actual parameters.

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 core verb+resource (find YouTube videos by keyword) is clear, but the description opens by claiming it can 'retrieve timestamped transcript segments by video ID', a mode the schema cannot support (only a free-text 'query' parameter exists). That claim also overlaps with the sibling youtube_transcript, so an agent cannot cleanly tell the two apart from the description alone.

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 a generic use case ('content research and summarization') but never states when to choose this over youtube_transcript or search_web, despite obvious overlap with both siblings. No exclusions or prerequisites are offered beyond the price note.

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