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

The description goes well beyond the annotations. It discloses that the tool 'moves real money', that it 'always requires the human — agents cannot change budgets', and details the per-send approval rail: each request queues its own approval card, sends exactly once on approve, and there is no standing grant. This is rich behavioral context that annotations alone do not provide.

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?

The description is compact and front-loaded with the core action, then the human-approval constraint, then usage guidance. The outbound-tier block is dense but every sentence carries operational weight. Slight redundancy between 'always requires the human' and the approval-rail detail, but no wasted words overall.

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 mutation tool with no output schema, the description covers the critical operational context: when to call, what happens on approval, the no-standing-grant rule, and the distinction from the Meta sibling. The annotations already declare destructiveHint=true and readOnlyHint=false, so the safety profile is clear. Nothing an agent needs to invoke this correctly is missing.

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 100%, so the schema already documents all parameters. The description adds context about the budget being in 'account currency, major units' and mentions the structural cap, which reinforces the daily_budget parameter, but it doesn't add meaning beyond what the schema provides for campaign_id, companyId, or ad_account_id. Baseline 3 is appropriate.

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 states a specific verb ('Change'), a specific resource ('daily budget of an X ads campaign'), and the currency/units ('account currency, major units; structural cap applies'). It also explicitly distinguishes itself from update_meta_ad_budget, so an agent can tell them apart without opening schemas.

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?

The description explicitly says when to use it ('when the user explicitly asks to raise or lower spend on an X campaign') and names the alternative ('Distinct from update_meta_ad_budget'). It also gives clear operational guidance: call on the first clear ask, do not re-ask in chat, and the approval card is the yes.

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