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

Annotations already flag destructiveHint=true and readOnlyHint=false, but the description goes well beyond them: it discloses that a checkpoint is taken first and the image is restored on failure, that on success the story persists as live layers, and that the result carries the checkpoint id. It also documents the safe-zone geometry (top 250 px / bottom 340 px unsafe bands) and the single-layer and panorama constraints.

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?

The opening sentence front-loads output type and dimensions, and every subsequent sentence carries required information (background modes, safe zone, constraints, checkpoint behavior). It is a dense single paragraph rather than organized sections, and the final checkpoint sentence is a run-on, which costs a point on structure.

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 still explains the returns: one download link plus the checkpoint id for the plain photo. Given seven parameters and destructive/open-world behavior, it supplies the constraints, defaults, and side-effect behavior an agent needs to call it correctly.

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 adds genuine meaning the schema lacks: blur defaults to a blurred scaled-up copy of the photo, gradient runs top-to-bottom with gradient_top defaulting to white and gradient_bottom to a 15% darker shade, and caption styling (white bold with black outline, fitted above the handle). This meaningfully extends the terse schema descriptions.

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 precise verb+resource ("Make a 9:16 story frame (1080x1920) from a photo") with exact output dimensions and format, which clearly separates it from siblings like make_meme, make_grid and make_carousel. An agent knows exactly what this produces without opening the schema.

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 clear operative context and constraints: the image must have a single layer, and a panorama (very wide/tall photo) cannot take the blurred background and must use a color or gradient. It never names a sibling alternative or explicitly says when another tool is preferred, so it stops short of explicit routing.

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