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

Annotations declare a destructive, non-read-only write; the description adds the material context behind that: overwrite semantics ('a day is set, not incremented'), the matching paths (launches, manual links, '(TID: N)' marker), unmatched rows being reported back, and the bad_currency rejection. The 'a day is set, not incremented' wording sits slightly at odds with idempotentHint=false, but the whole-send requirement per campaign-day explains why partial re-sends are unsafe, so this reads as clarification rather than contradiction.

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-loads the core action and the token-free mechanism, then layers constraints. It is a dense multi-clause sentence chain, but every clause carries operational weight; minor tightening of the parenthetical and dash structure would help readability.

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 destructive, batch-write tool with no output schema, the description covers mechanism, matching, overwrite rules, currency gating and unmatched-row reporting. Remaining gaps are minor: the shape of the unmatched-rows report and failure/partial-success behavior are not described, though the 5000 maxItems is covered by the schema.

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 75%, so the schema already documents the row fields; the description adds meaning on top by explaining why campaign_name matters (enables the (TID: N) fallback match) and why rows are keyed per day × campaign × ad set. It reinforces the currency restriction but says nothing extra about timezone or ad_account_id beyond the 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?

States a specific verb and resource — 'Book Facebook (Meta) daily spend into click costs' — plus the distinctive mechanism (rows scraped by the Torvex browser extension from a logged-in Ads Manager session). This clearly separates it from import_google_costs, set_campaign_costs, and the report_meta_* readers in the sibling list.

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?

Gives real preconditions: no Graph token needed, USD cabinets only, and the hard constraint that a request must carry every row of a FB campaign for the days it covers. It does not explicitly name the alternative tool to use when a Graph token/pull-based flow is preferred, nor when to prefer set_campaign_costs for manual entry, so full routing guidance is missing.

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