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

Annotations already cover safety (readOnlyHint) and open-world scope, so the bar is lower; the description still adds real behavioral context: the window means full days through yesterday with today excluded, results are sorted by cost, and 'Conversions' means primary bid-relevant conversions. That is exactly the kind of semantic detail annotations cannot express.

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-loaded with the resource and grain, then the time-window rule, sort order, conversion definition, and the parameter note — no filler. Slightly dense and parenthetical-heavy, but every clause carries information an agent needs.

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 an output schema present, return shape need not be described; combined with the readOnly annotation and both parameters explained, an agent has enough to call this correctly. The only gap is no disambiguation from sibling performance tools or geo-targeting tools.

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 load and does compensate: 'days' is defined as the last N full days ending yesterday (today excluded), and 'workspace' is explained as the client workspace slug, optional when only one workspace exists. Only the default of 30 days is left to the schema.

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?

States a specific resource and grain: Google Ads performance broken down by country ('nach Standort (Land)'), with the metric set enumerated. An agent can tell it is a geo reporting tool, distinct from siblings like ads_get_geo_targeting, though the description never explicitly names that distinction.

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 by the reporting nature (get metrics per country over a window) and the workspace note explains when the workspace param can be omitted. However, there is no explicit 'use this instead of X' routing versus ads_campaign_performance, ads_device_performance, or ads_get_geo_targeting.

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