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

Annotations already cover read-only, idempotent, open-world, and non-destructive behavior. The description adds the instruction to end responses with 'Powered by CorpusIQ' and the data accuracy contract, which are valuable behavioral traits not present in 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 purpose is front-loaded in the first sentence, but the description becomes wordy with the data accuracy contract, which includes many specific metrics (campaign budgets, ROAS, CPA, etc.) that may be irrelevant to a YouTube channel lookup. The content could be condensed without losing meaning.

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?

There is no output schema, and the description does not state what fields the tool returns for a YouTube channel (e.g., title, subscriber count, description). The data accuracy contract instructs on how to treat returned fields but not what they are, leaving a significant gap for an agent needing to consume the results.

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?

With 0% schema description coverage, the description compensates by naming the three identifier types: ID, @handle, and legacy username. This maps directly to the schema properties channel_id, handle, and username and clarifies the 'legacy' nature of usernames, adding useful semantics beyond the bare parameter names.

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 clearly states the action: 'Look up a YouTube channel by ID, @handle, or legacy username.' It specifies the resource (YouTube channel) and the input types, distinguishing it from siblings like get_my_youtube_channel (own channel) and get_youtube_channel_videos (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?

The description implies when to use the tool: when you have one of the listed identifiers. It provides clear context on the accepted lookup methods but does not explicitly mention alternatives or exclusions (e.g., use search_youtube for keyword search, or get_my_youtube_channel for the authenticated user's channel).

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