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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint=false, so the safety profile is covered; the description adds genuinely new context: 'Free, works without a key', which tells the agent no authentication is required. It also discloses the return shape including the meaning of safe-zone margins, though it says nothing about result size or ordering.

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?

Cost/auth information is front-loaded and the usage instruction comes last, so the structure is sensible. The middle sentence is dense with a nested parenthetical about safe-zone margins, which costs some readability but every clause carries information the agent needs.

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?

With no output schema, the description takes on the job of describing the return fields and does so, and it covers cost, auth, and downstream consumers. What remains unstated (ordering, whether the list is exhaustive) is minor for a small static enumeration 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?

The tool takes zero parameters, so there is no parameter semantics to explain; the baseline of 4 applies. The description instead spends its words on the response fields, which is the right allocation for a no-arg tool.

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 uses a specific verb (list) and resource (platforms), then enumerates the returned fields (id, name, aliases, expected aspect, safe-zone margins) so the agent knows exactly what the payload contains. It also names the consumer tools (burn_captions, shorts, preview, prepare_client_burn, plan), which separates it from the similarly named list_presets and list_voices siblings.

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 states the concrete trigger: 'Use it to map what the user said ("para Reels", "for YouTube Shorts") to an id', and it identifies which downstream tools accept the resulting value. That gives the agent both the when-to-use condition and the reason the output matters, leaving little to infer.

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