get_ads_campaign_metrics

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

With no annotations the description carries the full burden and does well: it discloses the 30-day default window, that some metrics (ACOS) may be absent ('when present'), and that scope errors surface clearly, which prepares the agent for auth failures. It omits pagination, rate limits, and whether it is strictly read-only, but the behavioral coverage is strong for a metrics getter.

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?

Front-loads the core purpose and metric list, with prerequisites layered after. The ACOS explanation sentence is useful sense-making but slightly expandable; overall it is dense and earns its length.

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?

No output schema exists, so the description compensates by naming the returned metrics (impressions, clicks, CTR, cost, attributed sales, ACOS). Combined with the default range and scope note, an agent has enough to invoke and interpret results, with only residual gaps around formatting and pagination.

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 the schema already documents campaign_id, date_from, date_to with their defaults. The description repeats the date format and 30-day default rather than adding new parameter semantics, making this the baseline 3.

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?

Specific verb+resource ('Get performance metrics of a Mercado Ads campaign') with the exact metric list enumerated, which distinguishes it cleanly from the sibling get_ads_campaigns that only supplies ids. An agent can tell what it returns without opening the schema.

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?

Explicitly frames the intent ('evaluate ad spend efficiency') and routes to get_ads_campaigns as the source for campaign ids, plus flags the required advertising scope. It stops short of stating when not to use it or naming a competing metrics tool, so it is a clear context without exclusions.

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