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

With no annotations, the description carries the full burden and does add two genuinely non-schema facts: a hard cap of 60 videos per page and a cost of 1 credit per call. It still omits auth requirements and what happens past the last page, so it is not exhaustive.

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?

Front-loaded with the verb+resource, then the page cap and billing, with a compact parenthetical field list. Three short sentences with no filler; the field list is dense but earns its place given there is no output schema.

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, enumerating returned fields (title, url, duration, views, etc.) plus the per-page limit and cost gives the agent enough to invoke and interpret results. Only minor gaps remain, such as pagination termination and region default behavior.

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 75%, which already documents q, time, region, duration, and safe_search; the description adds no parameter-level meaning (no defaults, no interaction between page and time, no region default). Baseline 3 applies when the schema does the heavy lifting.

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 names a specific resource (DuckDuckGo Videos for a query) and enumerates the fields returned, so an agent knows exactly what this tool produces. It is distinguishable from get_images/get_news/get_places by the vertical, but it never explicitly states the contrast the way a 5 would.

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?

Usage is only implied by the resource name — there is no statement of when to choose video search over the sibling news, images, or places tools, nor any prerequisite or exclusion. Adequate for a straightforward vertical search, but the agent must infer routing.

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