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

With no annotations provided, the description carries the full burden, and it does add real behavioral facts: the 0.25-4.0 operating range and that audio pitch is preserved (i.e., no chipmunk effect). It omits other traits an agent would want, such as accepted URL forms, whether processing is synchronous, and where the output goes.

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 short sentences with zero padding; the operation is stated first, then the quantitative convention, then the audio caveat. Every sentence earns its place.

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 two-parameter tool with no annotations and no output schema, the description covers the core mechanics but leaves the input side half-specified (undefined `url` format) and says nothing about the return value. Adequate to call correctly in the common case, incomplete for edge cases.

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 0%, so the description must compensate for both parameters. It handles `factor` well, giving the direction convention, concrete examples (2.0, 0.5), and the valid range, but leaves `url` entirely undefined — no indication of whether it is a remote link, a file ID, or an upload reference.

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?

"Speed a video up or slow it down" names a specific verb (speed) and resource (video), which is unambiguous against siblings like video_trim or video_concat. It stops short of explicitly contrasting itself with neighboring tools, but an agent can identify the operation immediately.

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 never states when to reach for this tool versus alternatives, nor any prerequisites or exclusions. The factor explanation is parameter semantics rather than usage routing, so the agent must infer applicability entirely on its own.

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