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

Annotations already cover read-only, idempotent, non-destructive behavior, so the bar is lower; the description nonetheless adds real context: hard caps on excerpt length (200 chars/40 words for articles, 300/60 for transcripts) with the rationale, plus an explicit 'no full transcript' limitation. It doesn't say how relevance/matching works or what happens when nothing matches.

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 with the core action, then two short sentences of size limits and rationale — each earns its place. The 'up to five' framing versus the limit parameter's default of 3 introduces avoidable ambiguity in an otherwise tight description.

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?

An output schema exists, so return shape needn't be explained. Still, for a 3-parameter tool with 0% schema coverage, the description leaves video_id undefined and the limit ceiling-vs-default relationship unclear, which an agent needs in order 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 0% for all three parameters. The description only gestures at 'query' and implies a ceiling of five results via 'up to five', which actually conflicts with the schema's default of 3 and leaves the limit semantics ambiguous. video_id is never mentioned at all, so the most important required input is unexplained.

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 ('Find ... short transcript or article excerpts supporting a query') and implicitly distinguishes itself from full-text tools by saying full transcript access is unavailable. It never names a sibling such as read_summary or search_insights, so the agent must infer differentiation.

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 phrase 'supporting a query' implies a verification/grounding use case, and 'full transcript access is intentionally unavailable' routes the agent away from a transcript-reading expectation. However, there's no explicit when-to-use vs. when-to-use-a-sibling guidance despite six siblings in the same domain.

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