youtube-mcp

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It adds value by stating the quota cost ('Costs 50 quota units'), which is crucial for rate-limiting awareness. However, it lacks details on permissions (e.g., if the user must own the playlist), error handling, or response behavior, leaving gaps in transparency for a mutation tool.

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 front-loaded with the core purpose and cost, followed by a clear 'Args' section for parameters. Every sentence earns its place: the first states the action and quota, and the parameter explanations are necessary due to 0% schema coverage. It's appropriately sized with zero waste.

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 the tool's complexity (a mutation with 2 parameters, no annotations, but an output schema exists), the description is partially complete. It covers the purpose, cost, and parameter semantics, but lacks usage guidelines and full behavioral details. The presence of an output schema means return values are documented elsewhere, so the description doesn't need to explain them, but other gaps remain.

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 0%, so the description must compensate. It adds meaning by explaining that 'playlist_id' identifies the target playlist and 'video_id' specifies the video to add, which clarifies the parameters' roles beyond their names. However, it doesn't provide format details (e.g., ID structure) or constraints, so it only partially addresses the coverage gap.

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 verb ('Add') and resource ('a video to a playlist'), making the purpose immediately understandable. It distinguishes this from siblings like 'create_playlist' or 'update_playlist' by focusing on adding content to existing playlists. However, it doesn't explicitly mention what distinguishes it from 'list_playlist_items' or 'update_playlist' in terms of scope, which prevents a perfect score.

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 no guidance on when to use this tool versus alternatives. It doesn't mention prerequisites (e.g., needing an existing playlist), exclusions (e.g., not for removing items), or comparisons to siblings like 'update_playlist' or 'list_playlist_items'. The agent must infer usage from the purpose alone, which is insufficient for optimal tool selection.

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