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

Annotations already establish that this is a read-only, idempotent, non-destructive, closed-world operation. The description adds meaningful behavioral context beyond those hints, especially the plan-dependent white-label vs preview behavior and the conditional inclusion of client_link.

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?

The description is front-loaded with the core return value and then adds the relevant conditional details. It is dense but mostly earns its length; the single long sentence is slightly harder to scan than a broken-out structure would be.

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 output schema, the description carries the burden of explaining what comes back, and it does so by naming the report categories and the client_link behavior. It is nearly complete for a simple read tool, though it does not clarify output structure or edge cases such as brand lookup failures.

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 100%, so month, brand_id, and brand_name are already well documented in the schema. The description reinforces the single-brand scope and default month, but it does not add syntax, validation, or selection rules beyond what the schema provides.

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 clearly states that it returns one brand's monthly report and enumerates the report contents, which is much more specific than the title alone. It does not explicitly contrast itself with nearby siblings such as get_post_performance, so it stops short of full sibling differentiation.

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 explains that the report is for last month or a supplied month, and notes the client_link condition, but it does not say when an agent should choose this over alternatives like get_post_performance or list_brands. There are no explicit when-to-use or when-not-to-use guidelines.

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