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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so the safe-read profile is covered. The description adds real context beyond that: the exact formulas used, the absence of licensed Pantone data, and the ICC/paper caveat. However, it does not cover the safety surface being annotated, and the formula detail is low-value to an agent deciding how to call it.

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 the purpose and accepted formats, and the disclaimer about licensed data is well placed. The inline formula string (K = 1 - max(R,G,B); ...) is dense and adds little for an agent choosing or invoking the tool.

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 a single required parameter, no output schema and read-only annotations, the description supplies everything needed: accepted input syntax, return contents, the spot-color fallback, and an accuracy warning. Nothing an agent needs to call it correctly 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% and the schema only says 'Hex, rgb() or cmyk()', so the description's concrete examples (#1a2b3c, rgb(26,43,60), cmyk(60,40,40,100)) add genuine formatting detail. It also documents the edge case of passing a spot name, which the schema does not express.

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 and resource ('Approximate between sRGB and CMYK'), names the accepted input formats, and enumerates what comes back (other model, total ink, gamut cautions). No sibling in the list performs bidirectional sRGB/CMYK conversion, so an agent can select it unambiguously from tools like check_colour_mode or chart_colour_check.

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?

Usage context is implied by the input formats and the spot-color aside, but there is no explicit 'use this when...' or named alternative among siblings. The one routing rule it does give — passing a spot name yields a lookup instruction rather than a value — is useful but narrow.

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