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

Goes well beyond the readOnlyHint/openWorldHint annotations: it discloses the cost ($0.002 USDC per successful call), the payment rails (x402 on Base, Solana or Arc), and that failed calls are not charged — exactly the kind of billing/charge semantics an agent needs before invoking a paid endpoint. It also clarifies the read-only boundary (metadata only, no file returned).

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 sentences, front-loaded with what is returned, then the access constraint, then pricing. Each sentence earns its place, though the field enumeration ('title, description, duration in seconds, size...') partially duplicates what the output schema already declares.

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 one-parameter read tool with an output schema and annotations, nothing material is missing: scope, access limits, cost and charge-on-failure behavior are all stated, so an agent can call it correctly and predict billing.

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 the single parameter is documented with its 32-character share-link format, so the schema carries the load. The description adds only marginally, via the access-level constraint that determines whether a given URL will succeed.

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?

Names a specific resource (Loom video metadata via oEmbed) and enumerates the returned fields (title, description, duration, size, thumbnail, embed URL). It also explicitly negates what the tool name implies — 'does not download or return the video file' — which is essential, though the name/title 'Downloader' remains misleading until the agent reads the description.

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?

Provides a precondition ('Works only for videos the owner made public or anyone-with-link') but never says when to choose this tool versus anything else, and names no alternative for the case where a private video must be handled. Usage is implied by the input being a Loom share link rather than stated.

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