subscribe_channel

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It only says 'Subscribe to a YouTube channel' and does not explain that this modifies the authenticated user's subscriptions, requires any authorization, or what the result/response will be. The description is minimal and largely restates the tool name.

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 a single, short, front-loaded sentence with no unnecessary words. For a one-parameter tool with no output schema, this level of conciseness is appropriate.

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?

The core purpose and parameter are covered, but with no annotations and no output schema, the description leaves out useful context such as authentication requirements, expected response, and whether subscribing is idempotent. It is functional for a simple action but not fully complete.

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 fully documents channel_id with its own description ('Channel ID or URL to subscribe to'), so schema coverage is 100%. The tool description adds no additional parameter-level meaning, so the 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?

The description states a specific verb ('Subscribe') and resource ('a YouTube channel'), making the tool's purpose immediately clear. This verb/resource combination also distinguishes it from the sibling tools, which are mostly search/get/list operations.

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 that the tool should be used when the user wants to subscribe to a channel, but it provides no explicit guidance about when not to use it or how it relates to alternatives like get_subscriptions. It relies on the agent to infer the usage context.

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