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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered. The description adds useful behavior beyond that: results are ordered by date and can be split per provider. It omits what happens when since/until are null (are defaults applied, or all-time?), and says nothing about result limits or pagination for a potentially large daily series.

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?

A single bracketed sentinel ('[read]') plus one dense sentence with no waste; the core purpose is front-loaded and the filter semantics follow immediately.

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 11-parameter tool with zero schema descriptions and no output schema, the description covers the ambiguous id/uuid duality and the split flag, which are the highest-risk unknowns. However, campaign_key is never mentioned, date formats and null-date behavior are unstated, and no hint is given about the returned point structure, leaving meaningful gaps.

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% across 11 parameters, so the description must carry the load — and it does the most valuable part by explaining that the website, account and customer filters accept either an id or a uuid, which is otherwise completely opaque from param names alone. It also clarifies split_by_provider and the date-range pair. It leaves campaign_key entirely unexplained and gives no date format for since/until, so it does not fully compensate.

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 — 'daily ad spend/result points for a date range' — plus ordering by date and an optional provider split, which distinguishes it from the summary and campaigns siblings by granularity. It does not name those siblings explicitly, so the differentiation is inferred rather than stated.

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 phrase 'daily ... points' and 'ordered by date' implies this is the choice for trend-over-time analysis, but there is no explicit when-to-use, when-not-to-use, or pointer to ads_insights_summary / ads_insights_campaigns as alternatives. Usage must be inferred from the word 'timeseries'.

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