Pick a colour

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

With no annotations, the description carries full behavioral burden and does disclose one useful trait: the value is applied via the element's own picker rather than by direct input simulation. It omits whether a picker surface/dialog appears, whether change/input events fire, and how failures on non-color elements are reported — meaningful gaps given a sibling 'dialog' tool exists.

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 short, front-loaded fragments with no filler, and the core action leads. The second fragment ("value as #rrggbb") is verbless and slightly telegraphic, costing a little clarity for its brevity.

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 two-parameter, no-output-schema tool this is nearly adequate, but it leaves out what an agent needs to call it reliably: whether the picker interaction is synchronous, what error surfaces for a non-color element, and whether the id must come from a prior listing call.

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 50%: 'id' is documented in the schema as a listing element id (e.g. a12), while 'value' has only a regex pattern. The description partly compensates by stating the human-readable "#rrggbb" format for value, but adds nothing about id sourcing or lookup.

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 specific verb ("Sets") and a specific resource ("an input of type color"), which distinguishes it from the generic 'type' sibling that would target other inputs. The added detail that it goes "through its own picker" further narrows what this tool uniquely does.

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 is only implied: an agent can infer this is for color inputs rather than text fields, but the description never says when to prefer it over 'type' or 'select', nor what happens if the element is not a color input. No explicit when-not or alternative routing is given.

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