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

Annotations already establish readOnlyHint and openWorldHint, lowering the disclosure burden. The description adds valuable behavioral context: the time window is last N complete days through yesterday, today is excluded, and conversions refer to primary bid-relevant conversions. It does not cover rate limits or auth, but the added data-freshness and metric semantics are substantive.

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?

Four short lines, front-loaded with the core purpose, followed by time-window, metric, and workspace clarifications. Every sentence carries useful information with no filler.

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?

For a two-parameter read-only performance query with an output schema, the description is complete enough. It establishes scope, time window, conversion definition, and workspace semantics, which are the main interpretive details an agent needs before calling it.

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 compensate. It does: days is implicitly defined by 'letzte N vollständige Tage bis gestern', and workspace is explained as the customer workspace slug, optional when only one workspace exists. Defaults and valid ranges are still 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 analysis: performance by weekday and hour at account level. The dimension 'nach Wochentag und Stunde' clearly distinguishes it from sibling performance breakdowns like device or geo performance, so an agent can identify its role 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?

Provides clear context for when to use it: answering 'when does the account perform best?' with a defined time window. It does not explicitly name alternatives or exclusions versus other ads performance tools, but the intended analytical use case is clear.

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