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

Annotations already declare idempotentHint=true and destructiveHint=true, so the safety profile is covered; the description instead adds the non-obvious guarantee that the underlying event name is immutable, which is what makes repeated renames safe for funnels and alerts. It also discloses the reset semantics of null on display_name/color, which is the concrete 'destructive' behaviour. It does not contradict destructiveHint=true — null overwrites existing values.

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?

Front-loaded with the four mutation cases, then the immutability reassurance, then the operational rules. The eight-colour list is long but is the sole documentation of valid values, so it earns its space; the sentence could still be tightened, e.g. by pairing hexes without the parenthetical names.

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 6-parameter mutation with no output schema and annotations covering safety and idempotency, the description covers nearly everything an agent needs: what each field means, the valid colour values, reset semantics, and how to obtain the goal name. The remaining gap is the site parameter / multi-site scoping and any hint about what is returned after the update.

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?

At 50% schema coverage the description has to carry weight, and it does: it defines display_name, color, hidden and kpi in prose and supplies the full colour palette (Mint/Sky/Ice/Amber/Coral/Violet/Rose/Lime with hex values) that the schema leaves as a bare maxLength-7 string with no enum. Only the site parameter is left unaddressed, which the schema partly documents.

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 opening sentence names the exact mutation surface in concrete terms: rename via display_name, set colour, hide, or promote to #1 KPI. It also draws a sharp boundary the title alone obscures — 'the event name never changes' — and names list_goals as the read counterpart, so an agent can separate it from siblings.

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?

'Send only what changes' tells the agent this is a partial update, and 'null resets display_name or color' disambiguates the null path that would otherwise be a guess. 'Get names from list_goals' handles the lookup prerequisite. No explicit when-not-to-use or precondition (permissions, site scoping) is stated, which keeps it one notch below the top.

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