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 full computed surface (luminance, WCAG ratios with AA/AAA flags, recommended text color, tint/shade scale), which signals a pure read-only analysis operation with no side effects. It stops short of stating that there is no persistence or state change, but the nature of the tool makes that low-risk.

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 tight sentences: the first is a front-loaded what-it-does plus output list, the second is the usage cue. No filler, and the most scannable information (analyze a color, returns contrast data) leads.

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 must explain return values — and it enumerates them completely (hex/RGB/HSL, luminance, contrast ratios with pass flags, recommended text color, tint/shade scale). Combined with the tiny two-param surface, an agent has everything needed to select and invoke 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 description coverage is 100% and both parameters (color, locale) are documented in the schema itself, so the description adds little param-level meaning beyond repeating the accepted color formats. Baseline 3 is appropriate when the schema does the heavy lifting.

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?

Uses a specific verb ('Analyze') on a specific resource ('a color given as hex, rgb() or hsl()') and enumerates the exact outputs, making it easy to tell apart functionally from color-palette (palette generation) and color-blindness (simulation). It never names a sibling explicitly, so it stops just short of full sibling differentiation.

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 closing sentence gives an explicit use condition: 'Use this when a user asks to convert a color or to check color accessibility/contrast.' That is clear routing guidance, but there are no when-not conditions and no named alternatives (e.g., color-palette) for overlapping color requests.

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