Check an element against a placement safe area

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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description goes further: it enumerates the three verdict values, explains that 'unknown' means the platform publishes no fixed safe area (TikTok) and returns a reason instead of a guess, and states the two error conditions (unknown placement id, non-positive box size). This is behavior an agent cannot infer from the schema.

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 tight sentences, front-loaded with the core check and its result, followed by the routing hint and edge-case behavior. Every clause — units, verdict values, the TikTok fallback, error cases — carries information an 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 an output schema present the description needn't explain return shapes, yet it already summarizes the verdict values. Combined with the stated error conditions and coordinate frame, an agent has everything needed to call this correctly against any of the fourteen placements.

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 coverage is 100% and already documents each of the five parameters with units and the enum list, so the description only echoes the coordinate framing ('in px on the placement's own frame, origin top-left') and the positive-size requirement already encoded as minimum:1. Baseline 3 is appropriate; no new per-parameter syntax or defaults are added.

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 and resource: check whether a rectangle stays inside a placement's published safe area, with units and coordinate frame spelled out. It is immediately distinguishable from sibling get_social_media_placement, which it names as returning raw insets rather than a verdict.

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 says when to use it ('validate a layout before export') and names the alternative with its different purpose ('use get_social_media_placement for the raw insets'). The routing decision is fully determined.

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