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

Annotations already declare destructive=true and idempotent=true. The description still adds real context beyond them: the concrete effect (screens revert to scheduled content immediately) and an explicit authorization requirement (screen.cast), which annotations do not convey. It stops short of covering failure modes or partial-success semantics, so it is not a 5.

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?

Three dense sentences, front-loaded with the action and scope. The per-screen warning and the auth requirement are parenthetical and each earn their place with no 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?

An output schema exists, so return values need not be explained. For a single-parameter mutation the agent gets the effect, the permission needed, the idempotency behavior, and the correct identifier source — nothing material is missing.

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 a 3 is the baseline. The description goes further by stating the parameter accepts either the returned castId or the creativeId/contentId of the content being cast, and by clarifying that one cast covers all its screens — semantics that help the agent supply the right value.

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?

States a specific verb+resource (end a cast) and immediately scopes it: it ends the cast on EVERY screen it covers, and the covered screens go back to scheduled content. This distinguishes it from siblings like cast_content/quick_post, which create casts rather than terminate them.

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?

Explicitly tells the agent where the castId comes from (quick_post or cast_content), warns against the common wrong pattern (do not call once per screen), and notes that ending an already-ended cast succeeds. These are concrete when/how-to-invoke instructions, not inference.

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