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

With no annotations, the description carries the full burden. It discloses that the tool reads from a server-side cache, does not fetch arbitrary YouTube videos, and returns both metadata and transcript. It does not explicitly describe missing-id or error behavior, but the main operational behavior is clearly stated.

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?

Two sentences, front-loaded with the core operation, followed by scope exclusions and ID discovery guidance. Every sentence earns its place with no repetition or filler.

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?

For a simple id-based retrieval tool with two well-documented parameters, the description fully equips an agent: it states the return content (metadata plus transcript), the cache boundary, the exclusion of general YouTube search, and how to obtain valid ids. No output schema is needed because the return shape is adequately described.

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 100%, so the schema already documents both id and transcript_chars thoroughly, including defaults, bounds, and the 0-for-metadata-only behavior. The description adds little beyond reinforcing the metadata-plus-transcript idea, which is already in the schema.

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 names a specific verb ('Get'), a specific resource ('one Celestia-related YouTube video cached on this server'), and the key scope distinction (by video id, metadata plus transcript). It differentiates itself from generic YouTube fetching and from sibling tools like list_videos or search.

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?

It clearly states when to use the tool (for cached Celestia videos by id), when not to use it (arbitrary YouTube videos or searching YouTube at large), and provides explicit routing: use a dedicated YouTube tool for general video tasks, and find ids via list_videos or search.

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