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

The description discloses important behavior beyond the annotations: it does not download media, it rejects certain content types, and returned creator titles are untrusted data. These are non-obvious traits that materially affect how the agent should interpret results, and none contradict the annotations.

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 four compact sentences with no filler. The core behavior and constraints are front-loaded, and each sentence contributes necessary information about output, limitations, data trust, or usage permissions.

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 single-parameter, read-only, idempotent tool with no siblings and no output schema, the description covers everything an agent needs: what it does, what it returns, what it won't process, and when it should be used. Nothing critical is missing.

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 schema already fully documents the single parameter as a 'Public HTTPS Facebook video or Reel URL' with 100% coverage. The description reinforces that the URL should be public and user-provided, but it does not add significant new parameter-level semantics beyond the schema.

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 uses a specific verb ('Resolve') and identifies the exact resource ('public Facebook video or Reel URL') and deliverable ('MP4 download options with sound'). It clearly distinguishes the tool's purpose from merely downloading media, even without siblings to differentiate against.

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 explicitly states when the tool is appropriate ('Use for videos the user owns or has permission to save') and lists exclusions ('Private, login-only, live and DRM content are not supported'). This gives an agent enough context to decide when to invoke it.

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