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

Annotations only give readOnlyHint=false, destructiveHint=false and openWorldHint=true. The description adds genuinely new behavior: it reads current Meta settings, writes an approval draft, returns approval_ref and plan_digest, and critically 'This call does not change delivery' — the two-phase prepare/confirm contract that the annotations do not express.

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?

Four short sentences, front-loaded with what the tool does, then the return keys, then the safety note, then the alternative. No filler; every clause carries routing or safety information.

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?

Output schema exists so return values need not be detailed, and the description still names the key returned fields consistently. The workflow, non-effect, and next step are covered; the only real gap is parameter-level detail for an opaque connection_context and daily_budget format.

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 0% for 4 parameters, so the description carries the burden. It only implies campaign_id, daily_budget and ad_account_id through prose and says nothing about the daily_budget number format, ad_account_id semantics, or the connection_context token pattern — the least obvious parameter is entirely unexplained.

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, resource and scope: 'Prepare one campaign daily-budget change'. The word 'one' implicitly separates it from the batch sibling campaigns_prepare_budget_changes, and 'campaign' separates it from adsets_prepare_budget_change. An agent can identify the target operation without opening the schema.

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 names the follow-up tool ('apply only after approval with operations_confirm_campaign_budget') and the alternative for a different case ('Prefer entities_prepare_update for new work'). The when, the when-not, and the workflow ordering are all stated.

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