Palette from a reference image

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

Annotations already cover the safety profile (readOnly, idempotent, closed-world), and the description adds real context beyond them: colors are returned most-common-first, each tagged with a role, and delivered as "palette" and "legend" keys. It doesn't discuss failure modes for non-PNG or missing paths, but for a read-only tool this is solid disclosure.

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 dense sentences that front-load the core action and then the usage hint; every clause earns its place. The nested quotes around "palette"/"legend"/"~" add a little visual clutter but no real padding.

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?

An output schema exists, so return values needn't be spelled out, yet the description still conveys the ordering and role semantics that matter for downstream use. Combined with annotations covering safety, an agent has what it needs to call and interpret the tool 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 description coverage is 100% and both parameters (path, colors) are fully documented in the schema, so baseline 3 applies. The description never mentions the colors-count parameter or its bounds, adding no meaning beyond the schema.

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 gives a precise verb+resource ("Read a reference PNG ... and return its main colors") plus the exact output shape (a spec "palette" and "legend"). It implicitly separates itself from texel_import_png by clarifying the return is a palette with role-annotated colors, though it never names a sibling explicitly.

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?

It states a clear use case ("Use it to match a reference instead of guessing hex values") and a follow-up workflow ("derive the other tones with '~' steps"). It does not name the alternative tools an agent might pick instead, so it stops short of full when/when-not routing.

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