util_cbc

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

Annotations already state readOnlyHint=false, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds nothing beyond that: it does not say that existing colour schemes are overwritten, that the change persists in the session and in saved files/sessions, or whether an undo exists — the kind of context that matters for a state-mutating colour command.

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?

It is short and front-loaded, but the parenthetical duplicates the name verbatim and consumes half of the text without adding information. Brevity here reflects under-specification rather than efficiency.

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?

The tool has an output schema and just one optional parameter, so full detail is not required, but the description still omits what happens to pre-existing colours, what happens when no selection is given beyond the schema default, and how it differs from the other colour-by-* utilities in a very crowded sibling set.

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 single optional parameter already carries the description "What to recolour. Defaults to everything." The tool description adds no further meaning — it does not explain whether the value is a chain ID, a comma list, or a selection expression, which is the main ambiguity an agent would face.

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?

"Colors by chain" names an action and a target, so an agent can guess it is a PyMOL recolouring utility. But the parenthetical "(Color By Chain)" merely restates the name, and nothing distinguishes it from the many siblings (util_cbam, util_cbay, util_cbas, util_color_by_element, util_chainbow, spectrum, color) that also assign colours.

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?

There is no guidance on when to prefer this over util_color_by_element, util_chainbow, spectrum, or plain color, nor on prerequisites such as objects needing to be loaded. The agent must infer usage entirely from the name.

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