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

Annotations already cover read-only, idempotent, non-destructive, closed-world behavior, and the description adds real context beyond them: the two upstream sources, the EU/commercial-ads coverage restriction, and newest-first ordering. What it leaves out is pagination behavior and any rate/volume limits implied by the cursor/limit parameters.

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?

Two dense sentences with no filler, and the core purpose plus sort order are front-loaded. The field list is slightly run-on, but every element earns its place by compensating for the absent output schema.

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 5-parameter read tool with no output schema, the description covers source scope, sort order, returned fields, status values, and tier gating. Pagination semantics for cursor/limit are the remaining hole, but an agent has enough to call it correctly.

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%, so the description carries the full burden, and it mostly does not: appId, limit, and cursor get no explanation at all. 'EU countries' usefully scopes the country parameter and 'newest first' implies cursor ordering, but 'status is active or ended' merely restates the schema enum.

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 verb+resource (ad creatives for one app) and even discloses the upstream sources (Apple Ad Repository, Meta Ad Library). That is enough to separate it from siblings like get_app_creative_history or creative_changes, although it never explicitly contrasts itself with them.

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?

Usage is implied rather than stated: an agent can infer 'call this to see an app's ad creatives', and 'Pro only' communicates an access prerequisite. There is no explicit when-not guidance or reference to the overlapping siblings (creative_changes, get_app_creative_history), which is the main gap.

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