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

Annotations already declare destructiveHint=true and idempotentHint=true, so safety is partly covered. The description still adds the single most valuable non-obvious fact — that renaming does not cascade to story label associations — which an agent could not infer from schema or annotations. It is silent on permissions, failure modes for an unknown labelId, and whether omitted fields are left untouched.

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 with zero filler: the capability first, then the caveat and its escape hatch. Every clause earns its place, and the critical warning is not buried at the end of a long preamble.

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 three-parameter label mutation with no output schema, the definition covers purpose, the surprising semantic gap, and the migration path. It lacks only partial-update semantics and error behavior for an invalid labelId, which are minor given the schema clearly marks only labelId as required.

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 67% and the two optional fields (name, color) are directly implied by the description's 'rename... or change its color' phrasing. However, it does not state that the update is partial (omitted fields unchanged) or that at least one of name/color should be supplied, and the undescribed `name` parameter gets no compensating detail. Baseline 3 fits.

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 and resource pair — 'Rename a label or change its color' — which maps exactly to the two optional parameters. It is trivially distinguishable from create_label, delete_label, and list_labels, and it names the sibling that handles the adjacent concern (bulk_update_stories).

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?

Explicitly defines the boundary of the tool: it changes the Label row only, and cross-references bulk_update_stories with labels.mode=replace as the route for migrating story-side references. That is a concrete when/when-not plus a named alternative with the exact parameter to use.

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