youtube_channel: GET /

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

Annotations are absent, so the description carries the full burden. It discloses the return shape across tabs and mentions pagination token availability indirectly via the parameter, but it does not describe rate limits, errors, or the fact that the operation is read-only (though 'Fetches' implies it). The behavioral disclosure is adequate but not exhaustive for a tool with no annotation support.

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 description is well-structured, starting with a concise summary ('Get YouTube Channel Data') and then expanding into function and use cases. Though it is longer than minimal, every sentence adds relevant information—the tab enumeration, return fields, and practical applications. It is front-loaded and avoids fluff, earning a 4.

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, the description must explain the return structure, which it does in detail by listing channel identity fields and tab-specific content types. It also covers the main use cases and even hints at integration with other endpoints. It does not cover pagination behavior beyond mentioning the token, but the schema already documents the parameter. Overall, the description is comprehensive for the tool's complexity.

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?

The input schema already provides 100% description coverage for all parameters, including detailed explanations for both `tab` and `channelId`. The description adds value by contextualizing the tool's use cases (e.g., feeding IDs to other endpoints) but does not contribute new parameter-specific semantics beyond the schema. Baseline 3 is appropriate given high schema coverage.

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 opens with a specific verb ('Fetches') and resource ('YouTube channel by ID or handle'), enumerates the supported tabs, and details the returned data (channel identity, counts, social links, tab items). It also clearly distinguishes this tool from siblings by noting it can 'feed videoId into the YouTube Video / Transcript endpoints.' This leaves no ambiguity about what the tool does or how it differs from search, transcript, and video tools.

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 provides clear use cases (monitor competitor channels, build directories, track growth signals) and implies when to use it relative to the video/transcript endpoints. However, it does not explicitly state when NOT to use this tool or directly compare it to the sibling search tool. The context is clear and actionable, but exclusions are left implicit.

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