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

Annotations already declare read-only and non-destructive, but the description adds meaningful behavioral context: requires an API key, credit charge per video including repeat calls, free skipping for videos without captions, typical cost for 10 videos, and a rate limit of 5 requests per 10 seconds. This goes beyond annotation defaults and enriches the agent's understanding of side effects and constraints.

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?

Every sentence earns its place: purpose, usage guidance, cost model, and rate limit are all packed into a few clear sentences. Information is front-loaded with the core function before operational details, with no filler or repetition.

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 description is fully self-contained for selecting and invoking the tool: it specifies output format, input scope, cost behavior, exclusions (videos without captions), rate limiting, and sibling alternatives. Output schema exists, so return-value detail is not required. It covers all essential operational and selection dimensions for a non-trivial tool.

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 already documents both parameters well (100% coverage), so baseline is 3. The description adds value by tying 'limit' to credit costs ('A 10-video call typically costs up to 10 credits, so start with a small limit') and providing example URL formats, giving practical semantics beyond the schema alone.

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 precise verb and object: 'Get transcripts for a YouTube channel's most recent videos (newest first) as timestamped markdown, one section per video.' It clearly distinguishes from siblings by specifying channel-level scope and explicitly contrasting with get_transcript for a single known video.

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?

Provides explicit usage context: 'Use for research across a creator's recent output' and names the alternative 'for one known video use get_transcript.' Also includes practical operational guidance on credits and rate limits, which helps the agent decide when and how to invoke it.

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