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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, covering the safety profile. The description adds minimal behavioral context beyond that, only implying a conversion operation. It does not specify the return format or any edge cases, so the burden on the description is low given annotations, but it does not add rich context.

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 sentences with no filler. The primary action is front-loaded, and the critical usage constraint is stated immediately. Every word earns its place.

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?

For a simple three-parameter tool with no output schema, the description covers the essential purpose and the exclusivity rule. However, it does not describe the output format (e.g., what the converted values look like), which is a minor gap. Given the tool's simplicity, this is nearly complete.

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%, with each parameter already documenting its format and the exclusivity rule. The tool description merely restates the exclusivity constraint, adding no new semantic information beyond the schema. Baseline of 3 is appropriate when the schema fully documents parameters.

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 states a specific verb ('Converts'), a resource ('color'), and the exact formats involved (hex, RGB, HSL). This clearly distinguishes it from all sibling tools, which are unrelated utilities. No ambiguity about the tool's function.

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 description explicitly instructs the caller to 'Provide exactly one of hex, rgb or hsl', which is clear usage guidance. It does not mention alternatives because none exist among siblings, but the exclusivity constraint is stated both in the description and schema, making the usage rule unambiguous.

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