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

The description asserts a read-only profile ('Read ... Does not modify advertising') while the annotation explicitly sets readOnlyHint=false, so the description contradicts the structured behavioral signal an agent would otherwise trust. It also says nothing about the 'fresh' parameter's refresh behavior, rate limits, or whether results are cached, leaving the side-effect profile actively misleading rather than merely incomplete.

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 short sentences, front-loaded with the verb and resource, with no filler. The second sentence is arguably a waste since it restates the read-only claim already (incorrectly) implied by 'Read' and adds no new information.

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?

Because an output schema exists, return-value documentation is not needed, but for a six-parameter tool with one required enum and zero schema descriptions the description is far too thin. An agent cannot infer valid dimension semantics, date-range rules, account limits, or the effect of 'fresh' from what is provided.

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 six parameters, so the description must carry the semantics and largely does not. It gestures at accountIds ('selected ad accounts') and since/until ('completed dates') but never explains the required 'dimension' enum values, the meaning/units of the breakdown, or what 'fresh' toggles.

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 concrete verb and resource ('Read a Meta advertising breakdown') and scopes it to ad accounts and completed dates, which is specific enough to separate it from generic reads like get_analytics. However, it never names the closest siblings (get_ad_performance, get_ad_campaign) or states how a 'breakdown' differs from them, so differentiation relies on the enum in the schema rather than the prose.

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 when-to-use guidance: no statement of when a breakdown is preferable to get_ad_performance or get_analytics, no prerequisites, and no exclusions. The only usage-shaped hint is the phrase 'completed dates', which obliquely implies that in-flight dates are not usable but never says so outright.

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