list_subscriptions

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

Annotations already provide readOnlyHint=true and openWorldHint=true, indicating a safe read operation. The description adds value by specifying the returned data structure (snippet and contentDetails fields) and the authentication modes. It does not contradict annotations and provides useful behavioral context beyond 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 description is three sentences with no redundant information. It is front-loaded with the core functionality, then details returned fields, then additional parameter uses. Every sentence is substantive and earns its place.

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?

Given no output schema, the description explains the return fields (snippet with title, description, resourceId.channelId; contentDetails with totalItemCount, newItemCount). It covers all parameters and authentication. The tool is relatively simple with 5 parameters, and the description provides complete context for an AI agent to use it correctly.

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?

All 5 parameters have descriptions in the schema (100% coverage). The description adds extra semantic meaning: e.g., channel_id requires API Key, mine requires OAuth, for_channel_id checks subscription status, page_token for pagination. This enriches the schema information.

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 tool lists subscriptions with two distinct modes: by channel_id for public subscriptions (API Key) or own subscriptions via mine=true (OAuth). It also specifies the returned fields (snippet, contentDetails) and additional parameters (for_channel_id, page_token). This specificity distinguishes it from sibling tools like list_channel_activities.

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 guidance on when to use each parameter: channel_id for channel subs, mine for own subs, for_channel_id for checking specific subscriptions, and page_token for pagination. It also mentions authentication requirements. However, it does not explicitly state when not to use this tool or suggest alternatives, but the sibling tools are distinct resources.

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