Channel performance over a date range

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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint. The description adds behavioral context beyond that, such as the YouTube Analytics 2-3 day lag on end_date and the row-count implications of group_by='day' or 'month' for long ranges. However, it doesn't describe the response structure or any edge cases like null metrics, which would be expected without an output schema.

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: the first lists the metrics, the second explains grouping, the third gives tool positioning. Every sentence serves a distinct purpose with no filler, front-loading the core function first.

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?

Despite the lack of an output schema, the description covers the core functionality, the main grouping option, and guidance on when to choose this tool over siblings. It omits details like exact response field names or pagination, but for an overview tool with strong annotations and schema, this is a reasonable level of completeness.

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%, with each parameter already having meaningful descriptions. The description's mention of group_by='day' or 'month' for a time series is essentially redundant with the schema. It adds no new semantic info beyond what the schema provides, so a baseline score of 3 is appropriate.

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?

Description uses a specific verb ('totals') and resource ('channel') with a clear scope ('over a date range'). It lists the metrics returned and explicitly distinguishes itself from traffic source and video-level tools, making it easy to differentiate from siblings like yt_traffic_sources and yt_top_videos.

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?

Explicitly states when to use it: 'This is the how is the channel doing tool — start with it, then drill into traffic sources or individual videos.' This gives clear usage context and names alternatives, satisfying the when-to-use vs alternatives guidance.

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