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

Annotations already declare readOnly/idempotent/non-destructive, so the bar is lower, yet the description still adds real behavior: it uses the calling user's stored Figma token (auth requirement), discloses truncation semantics ('truncated': true means more existed), and states that design units are points/dp at 1x and must be scaled by the device pixel ratio. None of that is available from the annotations.

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?

Front-loaded with what is returned, then usage, then input shapes, then output bounds, and finally the pixel-ratio TIP. The long field enumeration is dense but each item carries information an agent needs to interpret the payload, so nothing is 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?

With no output schema, the description carries the full burden of describing return values and does so in detail, plus covers auth, truncation, and unit-scaling. Nothing an agent needs to call and correctly interpret this tool 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 coverage is 100%, so the baseline is 3, but the description goes further: it clarifies the two accepted input shapes (a Figma link including node-id, or file_key + node_id) and explains what max_depth/max_nodes actually control and what truncation implies. It adds genuine cross-parameter meaning beyond the schema text.

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 ('Read the design details of a Figma frame as compact JSON') and enumerates exactly what the payload contains (id, name, type, bounds, text, font, fills/strokes, corner radius, auto-layout, style names). This cleanly separates it from the sibling figma_frame_image, which returns a picture rather than structured design data.

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?

Gives an explicit use case: verify copy, colours, fonts and spacing against what the device actually shows (page source / element bounds). That is a clear 'when to use' context, but it never names figma_frame_image as the alternative nor states when not to reach for this tool, so it falls short of the top band.

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