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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered. The description adds that results come 'with sources', which is genuinely useful provenance, but it does not say the data is static/hard-coded or what unit the margins are expressed in.

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?

A single front-loaded sentence with no filler; each clause (resolution, platforms, what is measured, sourcing) earns its place. It is dense but readable, with only slight cramming at the end.

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 parameters, no output schema and full annotation coverage, the description carries the return-value burden reasonably: it says it returns margins plus where buttons and captions sit, with sources. It could still state the response format or units, which is the only real gap for a zero-arg lookup.

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 nothing the description needs to disambiguate; baseline 4 applies. The description correctly adds no misleading input expectations.

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 and resource — returning safe-zone margins — and pins it to a concrete artifact (1080×1920 vertical video) and a named platform set (Instagram/Facebook Reels, TikTok, YouTube Shorts). That is far more specific than the sibling get_platform_specs, though it never explicitly contrasts itself with that tool.

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?

Usage is implied by the fixed context (vertical short-form video safe zones) rather than stated: there is no 'use this when', no exclusion, and no pointer to the nearby get_platform_specs or get_image_sizes siblings. An agent can infer applicability, but must guess whether specs and safe zones overlap.

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