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

With no annotations, the description carries the full burden and does well: it discloses the input size limit, the deliverables (before/after renders, size report, loader notes for three.js and Unity), and the billing model ($0.20 USDC via x402, charged only on success). It does not say whether the source asset is mutated in place or what happens on failure, which keeps it short of a 5.

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 core sentence is front-loaded and dense with useful detail, but the trailing 'Part of GLB optimizer: Make a GLB small and fast...' clause restates the same operations (dedup, join, simplify, textures, compression) already listed, adding length without new information.

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?

There is no output schema, so the description usefully sketches the returns and the pricing/size constraints. Still, for a 7-parameter, zero-required tool it omits how preset changes behavior and whether glb or glbUrl takes precedence, leaving an agent to guess on two decision points.

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 description coverage is only 29%, so the description must compensate. It effectively explains compression, textureFormat/maxTextureSize and simplifyRatio through its prose, but the preset parameter (web/mobile/preview) is never explained, and the relationship between the glb and glbUrl inputs is unaddressed.

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?

Specific verb and resource ('Shrink a GLB') plus a concrete scope constraint ('up to 10 MB') and an enumerated set of transformations (dedup, join draw calls, simplify, WebP textures, meshopt/Draco). The size cap implicitly separates it from the sibling glb_optimizer_optimize_large, though that sibling is never named.

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?

The target contexts ('for web or mobile') and the preset enum imply when to use it, and the 10 MB ceiling hints that larger assets belong to glb_optimizer_optimize_large. However, no alternative is named and there are no explicit exclusions or prerequisites, so routing is left to inference.

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