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

Annotations already flag destructiveHint=true and openWorldHint=true, so the mutation profile is known. The description adds genuinely useful behavior beyond that — the preview-then-confirm flow for extending a running ad set's end date, plus the lifetime-budget prerequisite for day-parting — but says nothing about reversibility, which ad set states are affected, or what the preview payload looks like.

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 sentences, no filler, and the primary capability is front-loaded before the caveats. The parenthetical and the confirm note each carry distinct operational information rather than restating the name.

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 an eight-parameter destructive mutation with no output schema, the description covers the two behaviors an agent would most likely get wrong: the confirm/preview flow and the lifetime-budget requirement. Time formats, mutual exclusivity of dates vs dayparting, and failure modes remain unaddressed, keeping it short of complete.

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 description coverage is only 38%, so the description must carry weight; it clarifies confirm (needed for the preview path) and day-parting semantics plus its budget precondition. However, adset, start_time, and end_time have no documentation anywhere — no timezone, format, or whether adset takes an ID or a name — which is a notable gap for a low-coverage schema.

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 description names a specific verb ('Change') and concrete resources: an ad set's start/end date and day-parting. That is enough to separate it from siblings like meta_update_budget or meta_update_targeting, though it never names those alternatives explicitly.

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?

It gives real conditional guidance: day-parting requires a lifetime budget, and extending the end date of a running ad set returns a preview and needs confirm=true. What's missing is routing against adjacent tools (meta_set_status, meta_update_budget) or what to do when neither dates nor dayparting are being changed.

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