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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is covered. The description adds value beyond that by disclosing the data provenance (most recent stored snapshot, i.e., potentially stale) and the result shape (one campaign set per connected ad account with named fields). It omits any note on pagination or behavior when no accounts are connected.

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 front-loaded sentence with no filler; every clause carries information (scope, provenance, per-account grouping, returned fields). It is written as a sentence fragment and leans on a long parenthetical, which slightly hurts readability but not economy.

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 parameters, no output schema, and rich annotations, the description covers the essentials: what is listed, where the data comes from, and which fields are present. Minor gaps remain around ordering, result volume for many accounts, and edge cases such as accounts without a stored snapshot.

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?

The tool takes zero parameters, so there is no parameter semantics to explain and the baseline of 4 applies. The parenthetical field list describes return content rather than inputs and does not conflict with the empty 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?

The description names a specific resource (campaigns) and a precise scope (most recent stored snapshot, one set per connected ad account), plus the fields returned. It is a noun phrase rather than a verb-led statement and does not explicitly differentiate itself from siblings such as list_ad_accounts or get_performance_summary, so it stops short of a 5.

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?

There is no explicit when-to-use or when-not-to-use guidance and no named alternative. However, the phrase 'most recent stored snapshot' implicitly signals that this returns cached/stored data rather than live queries, which is a usable signal when choosing between this and report-oriented siblings like get_latest_report or get_performance_summary.

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