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

Exceeds what annotations convey: merge is field-by-field with omitted fields preserved, decisions[] is left untouched, and the decision log caps at 50 with oldest dropped. That directly answers what a mutation with destructiveHint=true actually overwrites versus preserves, resolving the alarming annotation.

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?

Three front-loaded sentences, each adding distinct information: identity/scope, merge semantics, and timing plus the decision-log path. No filler or restatement of the title.

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 non-idempotent, destructive-flagged mutation with no output schema, the description covers persistence, merge behavior, and the decision log. It doesn't hint at what the call returns or any permission requirements, which is the remaining gap.

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%, but the description compensates by mapping the brief subfields to the domain and by explaining the decision/why split (choice in decision, reason in why). Only site_id and the 500-char limits are left solely to the schema, and those are trivial.

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 (set/incrementally update), a named resource (the durable site brief) and enumerates exactly what the brief holds (vibe, category, brand voice, palette/font names, tagline, audience). This distinguishes it clearly from sibling mutations like set_theme or update_page.

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?

"Call this once after picking a direction, then again whenever the direction shifts" gives concrete timing for invocation, and the decision/why sentence gives a second trigger. It stops short of naming alternatives (e.g., set_theme for palette changes), so no explicit when-not guidance.

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