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

Goes well past the annotations: states no writes and no guessed amounts, discloses pagination, specifies the comparison basis (latest two complete seven-day windows in account timezone), notes missing targets stay missing, warns that delivery targets are not profit, and lists what the report contains. Annotations already cover the safety profile, and the description still adds substantive behavioral context.

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 action, but the body is a dense chain of comma-spliced clauses ('Resolves the event and any cost-cap/minimum-ROAS delivery target from actual ad-set settings, never from generic results or its name') that take re-reading. The trailing MCP/credits boilerplate adds length without aiding tool selection.

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?

With no output schema, the description compensates by explaining that answer returns a report the agent writes the reply from and that the result includes gaps, evidence and a review point. It also flags read-only, no-guess behavior. Only the pagination/limit semantics and how multi-account runs are batched via evidence mode remain thin.

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?

Adds meaning beyond the 75%-covered schema by explaining the entityId/entityType pairing rule (omit both to discover owners, supply both to scope to one campaign/ad set) and by framing accountId/responsemode semantics in task terms. The limit/offset pagination pair and userStatement/idempotencyKey relevance are not addressed, which is acceptable for a read-only tool but leaves a gap.

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 opening states a specific verb and resource: evaluate budget-owning entities in one selected account and classify them maintain/increase/reduce/investigate. That is concrete and distinguishable from generic diagnostic siblings, though the opaque preamble 'After reading scaling-decision' and the dense middle sentences blur the core purpose. No sibling is named as the near-miss alternative.

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 usage conditions: omit entityId/entityType to discover owners rather than guess IDs, supply both to review a single campaign/ad set, and read recent changes and constraints before approval. It also explains when to pick answer vs evidence. It never names a sibling tool (e.g. planning_calculate, performance_diagnose) as the alternative, so routing is left partly to inference.

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