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

Annotations already declare readOnlyHint=true, idempotentHint=true and destructiveHint=false, so the appended 'READ-ONLY' is redundant confirmation rather than new information. The genuine additions are the empty-campaign_id scoping rule and the note that a per-type breakdown is available; nothing is said about result limits or pagination, which matters for an account-wide read.

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?

Three tight sentences with the scope statement front-loaded and no filler. The trailing 'by_type' sentence is slightly ambiguous — it reads like an output field rather than an instruction — but the definition is otherwise efficient.

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?

An output schema exists, so the description is not obliged to document return values, and it covers the tool's main variable behavior (campaign-scoped vs. account-wide). The remaining gap is the undocumented required customer_id and the absence of any pagination/volume caveat on an account-wide read.

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 must carry the load. It does explain that an empty campaign_id widens the query to the whole account, which is meaningful semantics beyond the empty-string default. However, the required customer_id parameter is never mentioned, and the stray 'by_type' reference does not correspond to any declared parameter.

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?

Names a specific verb and resource ('Reads the extension assets LINKED to a campaign') and enumerates the six asset types, so the agent knows exactly what is returned. It does not, however, distinguish itself from the nearby sibling list_extension_assets, which an agent could easily confuse with this tool.

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?

It provides one useful usage rule — omitting campaign_id returns extensions for all campaigns in the account — which is a real behavioral contract, not just a restatement. But it gives no guidance on when to prefer this tool over list_extension_assets, manage_extension_assets, or extension_asset_performance.

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