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

With no annotations provided, the description carries the full burden of behavioral disclosure. It thoroughly covers pay-per-call via x402 (USDC on Base), no account or API key requirement, error and non-charge behavior for invalid inputs, and the 60-minute length limit. This goes well beyond a simple action statement.

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 compact and front-loads the core purpose, then efficiently conveys critical operational details like payment, auth, error behavior, and length constraints. Every sentence adds distinct value with no filler, making it appropriately dense for a paid API tool.

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 simple 2-parameter tool with no output schema and no annotations, the description is remarkably complete. It covers purpose, output text, language selection, payment model, missing auth requirements, cost rationale, error cases, and length limits—everything an agent needs to decide and execute a call correctly. Schema defaults are rightly left to the schema.

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?

The input schema has no parameter descriptions, so the description must compensate. It adds meaning for the `language` parameter (100+ languages, BCP-47 format) and for `url` by explaining that bad URLs produce errors without charge. It does not fully elaborate on URL formats or the default language, but the schema already provides the default.

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 the tool's function: summarize a YouTube video and return the summary text, with a specific verb and resource. It does not explicitly contrast itself with sibling tools like get_youtube_transcript or list_new_channel_videos, so it falls short of a 5, but the action is 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 gives implicit usage guidance by noting it is cheaper than pulling the full transcript into your own context)Skip, and it specifies conditions under which it errors (bad URL, no captions, videos over 60 minutes, undeterminable length). However, it never explicitly states when to prefer sibling tools or what alternatives exist, leaving the guidance implied rather than direct.

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