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

Annotations cover the safety profile (readOnlyHint=true, openWorldHint=true), so the bar is lower; the description still adds real value by disclosing the billing model ('Cost: 1 credit, charged only when a call succeeds') and enumerating the returned fields. It lacks detail on failure behavior (what happens to the credit on error, unsupported URLs), keeping it just short of 5.

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?

Three tightly packed sentences: purpose and returns first, then routing guidance, then cost. Every clause carries distinct information with no filler.

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?

With no output schema, the description compensates by listing the exact return fields (title, duration, thumbnail, uploader, upload date, view count, platform, formats with sizes), plus cost and routing. An agent has everything needed to call it correctly and interpret the result.

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?

Only one parameter exists and schema description coverage is 100%, so the schema already documents 'url' fully. The description adds only a mild generalization ('any URL'), which is baseline-level value beyond structured data.

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 (Extract) and resource (video metadata, formats, thumbnail) from any URL, and explicitly names the sibling tools it is not (video-download, transcribe). An agent can distinguish this from the other 23 siblings at a glance.

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?

Gives the when ('inspect a video before downloading it') and both alternatives with their conditions ('To get the file use video-download; for what is said in it use transcribe'). Nothing is left to inference for tool selection.

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