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

Adds real behavioral context beyond the annotations: the exact cost model ('1 request of the monthly quota per successful call', failures not charged) and the underlying endpoint (GET /v2/search, tbm=vid). The annotations already flag a non-read-only, quota-consuming operation, and the description explains why, so the two are consistent rather than contradictory. It does not describe pagination or result-set limits, which the schema covers instead.

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?

Two tight sentences with the output shape front-loaded and the cost warning immediately after; nothing is padded. The endpoint/parameter fragment '(tbm=vid)' is slightly terse but still earns its place by pinning down the search vertical.

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 10-parameter, no-output-schema tool the description covers the essentials: what it returns, what it costs, and the endpoint. Parameter-level detail is fully delegated to a 100%-covered schema, so nothing critical is missing, though a note on pagination/result limits would round it out.

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 description coverage is 100%, so the schema already documents all ten parameters in detail (gl, hl, lr, tbs, cache, start, device, fields, location). The description adds only 'for a query', which duplicates the required q parameter. Baseline 3 is appropriate when the schema carries the parameter burden.

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 and resource ('Google video results for a query') and even names the returned fields (title, channel, length, link), so the agent knows exactly what comes back. It stops short of differentiating from the sibling zenserp_youtube_search, which an agent could easily confuse with this Google video-vertical search.

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?

Implies usage ('for a query') and adds a quota-discipline warning ('do not repeat a call needlessly'), which is useful operational guidance. However it gives no explicit when-to-use / when-not guidance against alternatives like zenserp_youtube_search, zenserp_image_search, or plain zenserp_search, leaving the routing decision to inference.

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